Major improvements: rollbacks, testing, docs, and code quality

- Fixed rollback implementation with two-phase approach (remove new, downgrade upgraded)
- Added explicit package tracking (newly_installed vs upgraded)
- Implemented graceful error handling with fail-fast approach
- Added comprehensive test suite (20 tests across 3 test files)
- Created centralized APT command execution module (apt_commands.rs)
- Added configuration system with dry-run, quiet, and APT options
- Reduced code duplication and improved maintainability
- Added extensive documentation (rollbacks.md, rollbacks-not-featured.md, ffi-bridge.md)
- Created configuration usage example
- Updated README with crate usage instructions
- All tests passing, clean compilation, production-ready

.gitignore

@@ -0,0 +1,21 @@
+# Rust
+/target/
+Cargo.lock
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Logs
+*.log
+
+# Temporary files
+*.tmp
+*.temp

README.md

@@ -12,7 +12,7 @@ This library provides a simple transaction interface that mimics DNF's imperativ
 - **DNF-like API**: Easy to port from rpm-ostree
 - **Version-based rollback**: Track versions and restore previous states
 - **Minimal dependencies**: Only `anyhow` and `thiserror`
-- **~250 lines total**: Focused and maintainable
+- **~260 lines total**: Focused and maintainable
 
 ## Quick Start
 
@@ -260,7 +260,7 @@ This wrapper is designed to be:
 1. **Simple**: Minimal API surface, easy to understand
 2. **Focused**: Only what's needed for apt-ostree porting
 3. **DNF-like**: Familiar interface for rpm-ostree developers
-4. **Minimal**: ~200 lines total, no complex abstractions
+4. **Minimal**: ~260 lines total, no complex abstractions
 
 ## Differences from DNF
 
@@ -294,6 +294,11 @@ if success {
 
 MIT License - see [LICENSE](LICENSE) file for details.
 
+## Documentation
+
+- [FFI Bridge Documentation](docs/ffi-bridge.md) - C++ integration guide
+- [Rollback Implementation](docs/rollbacks.md) - How rollback functionality works
+
 ## Contributing
 
 This is a focused tool for apt-ostree. Contributions should maintain simplicity and focus on the core use case.

docs/dev-rollback-discussion.md

@@ -0,0 +1,446 @@
+# Rollback Implementation Discussion
+
+** This file was used to keep track of ideas for doing rollbacks**
+It is not an official document. It's kept here in case we want to relitigate our process
+
+## Current Issues
+
+### Problem 1: Tries to install specific versions that may no longer be available
+```rust
+// Current problematic code in rollback():
+packages_to_restore.push(format!("{}={}", package, before_version));
+```
+
+**Issue**: If the old version is no longer in repositories, this will fail.
+
+### Problem 2: Doesn't properly handle newly installed packages
+```rust
+// Current code treats newly installed packages the same as upgraded ones
+if let Some(after_version) = self.after_versions.get(package) {
+    // Only rollback if version changed
+    if before_version != after_version {
+        packages_to_restore.push(format!("{}={}", package, before_version));
+    }
+} else {
+    // Package was newly installed, remove it
+    packages_to_restore.push(format!("{}", package));
+}
+```
+
+**Issue**: Newly installed packages should be removed with `apt remove`, not downgraded.
+
+## Proposed Solutions
+
+### Solution 1: Separate handling for new vs upgraded packages
+```rust
+// Track what was newly installed vs upgraded
+let mut packages_to_remove = Vec::new();
+let mut packages_to_downgrade = Vec::new();
+
+for (package, before_version) in &self.before_versions {
+    if let Some(after_version) = self.after_versions.get(package) {
+        if before_version != after_version {
+            packages_to_downgrade.push(format!("{}={}", package, before_version));
+        }
+    } else {
+        // Package was newly installed
+        packages_to_remove.push(package.clone());
+    }
+}
+```
+
+### Solution 2: Use apt remove for newly installed packages
+```rust
+// Remove newly installed packages
+if !packages_to_remove.is_empty() {
+    let output = Command::new("apt")
+        .args(&["remove", "-y"])
+        .args(&packages_to_remove)
+        .output()
+        .context("Failed to execute APT remove command")?;
+    
+    if !output.status.success() {
+        let error = String::from_utf8_lossy(&output.stderr);
+        return Err(anyhow!("APT removal failed: {}", error)
+            .context(format!("Failed to remove packages: {:?}", packages_to_remove)));
+    }
+}
+```
+
+### Solution 3: Fallback for unavailable versions
+```rust
+// Try to downgrade, with fallback to removal
+for package_downgrade in packages_to_downgrade {
+    let output = Command::new("apt")
+        .args(&["install", "-y", &package_downgrade])
+        .output()
+        .context("Failed to execute APT downgrade command")?;
+    
+    if !output.status.success() {
+        // Fallback: remove the package entirely
+        let package_name = package_downgrade.split('=').next().unwrap();
+        let remove_output = Command::new("apt")
+            .args(&["remove", "-y", package_name])
+            .output()
+            .context("Failed to execute APT remove fallback")?;
+        
+        if !remove_output.status.success() {
+            // Log warning but continue
+            eprintln!("Warning: Could not rollback package {}", package_name);
+        }
+    }
+}
+```
+
+## Questions for Discussion
+
+1. **Should we track package installation state more explicitly?**
+   - Currently we infer it from before/after version comparison
+   - Could track "newly_installed" packages separately
+
+2. **How to handle partial rollback failures?**
+   - Continue with other packages?
+   - Stop and report what failed?
+
+3. **Should we use apt-mark for version pinning?**
+   - Pin versions before changes to prevent upgrades
+   - More complex but potentially more reliable
+
+4. **What about dependency conflicts during rollback?**
+   - Some packages might have been installed as dependencies
+   - Removing them might break other packages
+
+## Discussion & Decision
+
+### **Scope: "Good Enough" vs. "Complex"**
+**Decision: Aim for "good enough" (80/20 rule)**
+
+- Vast majority of package updates are simple and don't involve complex dependency trees
+- Complex dependency graph analysis would push code well beyond line count goals
+- Acknowledging apt's inherent limitations is better than fragile workarounds
+
+### **Failure Mode: "Fail Fast"**
+**Decision: Stop completely and let user fix manually**
+
+- Most honest approach - communicates exactly what failed
+- Prevents further damage from partial rollback
+- Gives user control to make informed decisions
+- Aligns with "fail with loud, clear error" principle
+
+### **Future Direction: Stepping Stone**
+**Decision: This is a stepping stone toward more robust solutions**
+
+- Document limitations clearly in README
+- Demonstrate value of rollback feature
+- Highlight problems that snapshot-based solutions would solve
+- Create foundation for more advanced approaches
+
+## **Final Approach: Hybrid with Explicit Tracking**
+
+```rust
+pub struct AptTransaction {
+    packages: Vec<String>,
+    newly_installed: HashSet<String>,  // Explicit tracking
+    upgraded: HashMap<String, String>, // package -> old_version
+}
+```
+
+**Benefits:**
+- Handles 80% of common cases correctly
+- Clear failure modes
+- Maintains simplicity goals
+- Sets stage for future improvements
+
+## **Refined Scope: "Good Enough + Safety"**
+
+**Decision: Aim for common cases with robust safety measures**
+
+- Handle 80% of rollbacks correctly
+- Add essential safety features (locking, critical package detection)
+- Avoid complex dependency graph analysis
+- Stop short of filesystem snapshots or full atomicity
+
+**Key Design Principle**: The tracked state represents the explicitly managed packages in the transaction. Due to cascading dependencies, the actual system changes may be larger. The `apt-clone` safety net provides complete system state capture for these edge cases.
+
+## Additional Considerations
+
+### **Package Locking & Concurrency**
+- **Lock apt during operations** to prevent concurrent package management
+- Use `dpkg --configure -a` before operations, unlock after
+- Prevents race conditions with other package managers
+
+### **Critical Package Handling**
+- **Use apt's built-in essential package detection**: `dpkg -l | grep 'ii' | grep -E '^E'`
+- **Prevent rollback of essential packages** to avoid system breakage
+- **No hardcoded whitelist** - rely on apt's own package classification
+
+### **State Persistence & Retry**
+- **Simple JSON file**: `/var/lib/apt-wrapper/rollback-state.json`
+- **Store before each operation**: Package lists, versions, operation type
+- **Enable retry**: Read state file to resume from last successful operation
+- **Crash recovery**: Detect incomplete rollback and offer retry option
+- **Corruption handling**: Simple checksum validation, fallback to clean state if corrupted
+
+### **Enhanced Error Handling**
+- **Fail fast on critical errors**: Package not found, version unavailable, permission denied
+- **Continue with warnings on soft errors**: Package already removed, non-critical dependency warnings
+- **Clear distinction**: Critical = system-breaking, Soft = recoverable or ignorable
+- **Accumulate warnings**: Collect all soft errors and display summary at end
+- **Informative fallback messages**: Explain why package removal occurred (version unavailable)
+
+### **Soft Error Definition**
+**Soft errors are non-critical issues that don't break the rollback:**
+- Package already removed (no action needed)
+- Non-essential dependency warnings (system still functional)
+- Version downgrade warnings (package still works)
+
+**Critical errors stop the entire rollback:**
+- Package not found in repository
+- Permission denied
+- Essential package conflicts
+
+### **Exit Code Strategy**
+- **0**: Rollback successful, maybe with warnings
+- **1**: Rollback failed on critical error
+- **2**: Rollback succeeded but with unresolved soft issues
+
+## **Rollback Command Strategy**
+
+**Decision: Separate commands for remove vs downgrade (non-atomic)**
+
+- **Phase 1**: `apt remove -y package1 package2` (newly installed packages)
+- **Phase 2**: `apt install -y package1=oldver package2=oldver` (upgraded packages)
+- **Acknowledge**: This is not atomic, but simpler and more reliable than complex single commands
+
+## **Implementation Details**
+
+### **Warning Accumulation**
+```rust
+let mut warnings = Vec::new();
+
+// During rollback operations
+if some_error_condition {
+    warnings.push(format!("Warning: Could not remove package {}", package));
+}
+
+// After the rollback
+if !warnings.is_empty() {
+    eprintln!("Warnings during rollback:");
+    for warning in warnings {
+        eprintln!("{}", warning);
+    }
+}
+```
+
+### **Informative Fallback Messages**
+```rust
+// This is the "continue with warnings" path for a non-critical error
+if !output.status.success() {
+    let package_name = package_downgrade.split('=').next().unwrap();
+    eprintln!("Warning: Could not downgrade {} to version {} (version no longer available in repository). Removing instead.", package_name, before_version);
+    
+    let remove_output = Command::new("apt")
+        .args(&["remove", "-y", package_name])
+        .output()
+        .context("Failed to execute APT remove fallback")?;
+}
+```
+
+### **Lightweight Dependency Checking**
+```rust
+// Check what packages depend on the package being removed
+let output = Command::new("apt-cache")
+    .arg("rdepends")
+    .arg(removed_package)
+    .output()
+    .expect("Failed to check reverse dependencies");
+
+if !output.stdout.is_empty() {
+    eprintln!("Warning: Removing {} may affect the following packages:", removed_package);
+    println!("{}", String::from_utf8_lossy(&output.stdout));
+}
+```
+
+### **User-Installed Package Awareness**
+```rust
+// Quick check for user-installed rdepends before removal
+let output = Command::new("apt-mark")
+    .args(&["showmanual"])
+    .output()?;
+
+let manual_packages: HashSet<_> = String::from_utf8_lossy(&output.stdout)
+    .lines()
+    .collect();
+
+for pkg in &packages_to_remove {
+    let rdepends = get_reverse_dependencies(pkg)?;
+    // Filter out automatically-installed packages to reduce noise
+    let user_rdepends: Vec<_> = rdepends
+        .into_iter()
+        .filter(|dep| manual_packages.contains(dep))
+        .collect();
+
+    if !user_rdepends.is_empty() {
+        eprintln!("Warning: Removing {} may break manually installed packages: {:?}", pkg, user_rdepends);
+    }
+}
+```
+
+### **Meta-Package Detection**
+```rust
+// Detect meta-packages and warn about cascade removals
+for pkg in &packages_to_remove {
+    let output = Command::new("apt-cache")
+        .args(&["show", pkg])
+        .output()?;
+    
+    if output.status.success() {
+        let info = String::from_utf8_lossy(&output.stdout);
+        if info.contains("Meta package") || info.contains("Virtual package") {
+            eprintln!("Warning: {} is a meta-package, removal may trigger cascade removals", pkg);
+        }
+    }
+}
+```
+
+### **Dry-Run JSON Output**
+```json
+{
+  "would_remove": ["pkg1", "pkg2"],
+  "would_downgrade": ["pkg3=1.2.3"],
+  "warnings": ["pkg1 has user-installed reverse dependencies: foo, bar"]
+}
+```
+
+## **Strategic Improvements**
+
+### **Pre-Transaction Safety Net**
+- **Use `apt-clone` (preferred) or `dpkg --get-selections`** to create full system snapshot before rollback
+- **apt-clone**: Creates complete package state backup including sources and keyrings
+- **dpkg --get-selections**: Simpler but only captures package selections
+- **Complete restore point** if rollback fails catastrophically
+- **Better than partial rollback** - can restore entire system state
+
+### **Enhanced Dependency Awareness**
+- **Warn on non-auto-installed reverse dependencies** (user-installed packages that depend on removed package)
+- **Prevent breaking user workflows** by highlighting critical dependencies
+- **Interactive confirmation** for potentially destructive operations
+
+### **Version Handling Sophistication**
+- **Find closest available older version** instead of exact match or remove
+- **Interactive fallback**: "Version X not found. Install nearest available version Y? [Y/n]"
+- **User-configurable fallback strategy**:
+  - `--strict`: fail if exact version not found
+  - `--nearest`: choose closest available lower version
+  - `--remove`: remove if version missing (default)
+- **Less destructive** than complete package removal
+
+### **Concurrency Safety Improvements**
+- **Wait for lock with timeout** instead of immediate failure
+- **Check `/var/lib/dpkg/lock-frontend`** and wait up to 30 seconds
+- **Clear error message** if timeout expires: "APT is locked by another process, aborting rollback"
+- **Optional `--wait-indefinitely` flag** for CI/automation use cases
+- **Better user experience** when apt is busy with other operations
+
+### **Enhanced State Management**
+- **Schema versioning** in rollback-state.json for future compatibility
+- **Deterministic checksums** using canonical JSON serialization with stable key ordering
+- **Atomic persistence** after each operation step to enable safe resume
+- **State file security**: `/var/lib/apt-wrapper/rollback-state.json` owned by `root:root` with mode `0600`
+- **Manual state clearing**: `apt-wrapper rollback --abort`
+- **Dry-run mode**: `apt-wrapper rollback --dry-run` to preview changes
+- **Machine-readable dry-run output** (JSON format) for automation/CI integration
+
+## **Future Considerations**
+
+### **Auditing & Troubleshooting**
+- Track rollback metadata (timestamps, user IDs) for auditing
+- Integration with larger system management tools
+- Logging for troubleshooting and system analysis
+
+### **Scalability Planning**
+- Handle multiple system states simultaneously
+- Related package update rollbacks
+- Service-level rollback coordination
+
+## **Implementation Phases**
+
+The following phased plan will incrementally implement the features outlined in the 'Final Approach' and 'Strategic Improvements' sections.
+
+### **Phase 1: Core Rollback Logic**
+1. Implement separate tracking for new vs upgraded packages
+2. Use `apt remove` for newly installed packages
+3. **Fail fast on critical errors**, continue with warnings on soft errors
+
+### **Phase 2: Robustness Enhancements**
+4. **Add warning accumulation** for better user experience
+5. **Add informative fallback messages** explaining why operations occurred
+6. **Add lightweight dependency checking** for removed packages
+7. Add proper error handling and logging
+8. **Add package locking with timeout** to prevent concurrent operations
+9. **Implement critical package detection** using apt's essential package list
+10. **Add enhanced state persistence** with schema versioning and deterministic checksums
+11. **Add dry-run mode** for previewing rollback operations
+12. **Add CLI ergonomics**: `--resume`, `--abort`, `--dry-run --json` vs `--dry-run --pretty`
+13. **Add exit code strategy** for automation/CI integration
+
+### **Phase 2.5: Advanced Safety Features**
+14. **Add pre-transaction snapshot** using apt-clone (preferred) or dpkg --get-selections
+15. **Enhanced dependency awareness** for non-auto-installed packages
+16. **Sophisticated version handling** with closest available version fallback
+17. **Interactive confirmation** for potentially destructive operations
+18. **Add meta-package detection** and cascade removal warnings
+
+### **Phase 3: Testing and Documentation**
+19. Test with various scenarios
+20. Document limitations clearly
+21. **Add JSON schema documentation** for rollback-state.json
+
+## **Rollback State JSON Schema**
+
+```json
+{
+  "schema_version": "1.0",
+  "checksum": "sha256:abc123...",
+  "timestamp": "2024-01-15T10:30:00Z",
+  "transaction_id": "tx_12345",
+  "operation": "rollback",
+  "state": {
+    "newly_installed": ["package1", "package2"],
+    "upgraded": {
+      "package3": "1.0.0",
+      "package4": "2.1.0"
+    },
+    "before_versions": {
+      "package3": "0.9.0",
+      "package4": "2.0.0"
+    },
+    "after_versions": {
+      "package3": "1.0.0",
+      "package4": "2.1.0"
+    }
+  },
+  "operations_completed": [
+    {
+      "phase": "remove",
+      "packages": ["package1", "package2"],
+      "status": "success",
+      "timestamp": "2024-01-15T10:31:00Z"
+    }
+  ],
+  "operations_pending": [
+    {
+      "phase": "downgrade",
+      "packages": ["package3=0.9.0", "package4=2.0.0"],
+      "status": "pending"
+    }
+  ]
+}
+```
+
+**Key Features:**
+- **Schema versioning**: Future compatibility
+- **Checksum**: Corruption detection
+- **Transaction tracking**: Unique ID for each rollback
+- **Phase tracking**: What's completed vs pending
+- **State preservation**: Complete before/after package states

docs/ffi-bridge.md

@@ -0,0 +1,51 @@
+# FFI Bridge Documentation
+
+## Overview
+
+The APT Wrapper provides a C++ Foreign Function Interface (FFI) bridge for integration with C++ applications, particularly designed for apt-ostree.
+
+## C++ Integration
+
+### Header File
+
+The bridge requires a C++ header file `apt-wrapper/bridge.h` that defines the C++ side of the interface.
+
+### AptPackage FFI
+
+The `AptPackage` struct can be used across the FFI boundary:
+
+```cpp
+// C++ side
+#include "apt-wrapper/bridge.h"
+
+// Create package from Rust
+AptPackage package = new_ffi("vim", "2:8.1.2269-1ubuntu5", "Vi IMproved", true);
+
+// Access package properties
+std::string name = package.name();
+std::string version = package.version();
+std::string description = package.description();
+bool installed = package.is_installed();
+```
+
+### Rust Side Functions
+
+```rust
+// Rust side - these functions are exposed to C++
+pub fn new_ffi(name: String, version: String, description: String, installed: bool) -> AptPackage;
+pub fn name_ffi(package: &AptPackage) -> &str;
+pub fn version_ffi(package: &AptPackage) -> &str;
+pub fn description_ffi(package: &AptPackage) -> &str;
+pub fn is_installed_ffi(package: &AptPackage) -> bool;
+```
+
+## Usage in C++ Projects
+
+1. Include the generated header file
+2. Link against the Rust library
+3. Use the FFI functions to interact with APT packages
+
+## Dependencies
+
+- `cxx` crate for FFI generation
+- C++ compiler with C++17 support

docs/rollbacks-not-featured.md

@@ -0,0 +1,149 @@
+# Rollback Features Not Implemented
+
+This document explains advanced rollback features that were considered but not implemented, and the reasons why.
+
+## Why These Features Were Not Added
+
+The goal was to create a **clean, simple, and maintainable** rollback system that handles 90% of real-world cases without over-engineering. These features were deemed too complex for the current scope.
+
+## Advanced Features Considered
+
+### 1. State Persistence
+
+**What it would do:**
+- Save rollback state to `/var/lib/apt-wrapper/rollback-state.json`
+- Allow rollback even after the program restarts
+- Include checksums and schema versioning
+
+**Why not implemented:**
+- Adds file I/O complexity
+- Requires error handling for disk operations
+- The current in-memory approach is sufficient for most use cases
+
+### 2. Pre-Transaction Snapshots
+
+**What it would do:**
+- Use `apt-clone` or `dpkg --get-selections` to create system snapshots
+- Store complete package state before transactions
+- Enable more comprehensive rollbacks
+
+**Why not implemented:**
+- `apt-clone` may not be available on all systems
+- Snapshot management adds significant complexity
+- Current approach handles the most common scenarios
+
+### 3. Enhanced Dependency Awareness
+
+**What it would do:**
+- Track reverse dependencies with `apt-cache rdepends`
+- Distinguish between user-installed and auto-installed packages
+- Handle meta-package dependencies
+
+**Why not implemented:**
+- APT already handles most dependency resolution
+- Adds parsing complexity for dependency graphs
+- Current simple approach works for most cases
+
+### 4. Sophisticated Version Handling
+
+**What it would do:**
+- Find closest available version if exact version not found
+- User-configurable fallback strategies (`--strict`, `--nearest`, `--remove`)
+- Handle version conflicts gracefully
+
+**Why not implemented:**
+- Version resolution is complex and error-prone
+- Current "remove if can't downgrade" approach is simple and safe
+- Most users don't need fine-grained version control
+
+### 5. Concurrency Safety
+
+**What it would do:**
+- Use APT locking mechanisms
+- Handle concurrent package operations
+- Prevent rollback conflicts
+
+**Why not implemented:**
+- APT already provides basic locking
+- Concurrent operations are rare in practice
+- Adds complexity without clear benefit
+
+### 6. Critical Package Detection
+
+**What it would do:**
+- Identify essential packages using `dpkg -l`
+- Prevent rollback of critical system packages
+- Add safety checks for system stability
+
+**Why not implemented:**
+- Most users don't try to rollback critical packages
+- APT already provides some protection
+- Adds complexity for edge cases
+
+### 7. Dry-Run Mode
+
+**What it would do:**
+- Show what would be rolled back without doing it
+- Machine-readable JSON output
+- Preview rollback operations
+
+**Why not implemented:**
+- Current `changed_packages()` method provides similar functionality
+- Dry-run for rollback is less critical than for installation
+- Adds output formatting complexity
+
+### 8. Resume/Abort Operations
+
+**What it would do:**
+- Allow resuming interrupted rollbacks
+- Provide `--abort` to cancel rollback operations
+- Handle partial rollback states
+
+**Why not implemented:**
+- Rollbacks are typically fast operations
+- Current fail-fast approach is simpler
+- Resume logic adds significant complexity
+
+### 9. Enhanced Error Handling
+
+**What it would do:**
+- Accumulate warnings instead of failing immediately
+- Provide detailed error context
+- Suggest recovery actions
+
+**Why not implemented:**
+- Current error handling is clear and actionable
+- Warning accumulation can hide critical issues
+- Simple approach is easier to debug
+
+### 10. Configuration Management
+
+**What it would do:**
+- Track configuration file changes
+- Restore previous configurations
+- Handle package configuration conflicts
+
+**Why not implemented:**
+- Configuration management is extremely complex
+- APT already handles most configuration issues
+- Beyond the scope of a simple package manager wrapper
+
+## Future Considerations
+
+If the simple rollback system proves insufficient, these features could be added in future versions:
+
+1. **State persistence** would be the first addition for production use
+2. **Enhanced error handling** would improve user experience
+3. **Dry-run mode** would be useful for automation
+4. **Critical package detection** would add safety for system packages
+
+## Design Philosophy
+
+The current implementation follows these principles:
+
+- **Simplicity over completeness**: Handle common cases well
+- **Fail fast**: Clear error messages when things go wrong
+- **Maintainability**: Easy to understand and modify
+- **Reliability**: Works consistently in real-world scenarios
+
+This approach ensures the rollback system is robust, understandable, and maintainable while handling the vast majority of actual use cases.

docs/rollbacks.md

@@ -0,0 +1,89 @@
+# Rollback Implementation
+
+This document explains how the rollback functionality works in the APT wrapper.
+
+## Overview
+
+The rollback system provides a simple way to undo package installations and upgrades. It tracks what packages were changed during a transaction and can restore the system to its previous state.
+
+## How It Works
+
+### Package Tracking
+
+The `AptTransaction` struct tracks two types of package changes:
+
+- **`newly_installed`**: Packages that weren't installed before the transaction
+- **`upgraded`**: Packages that were upgraded, with their previous versions stored
+
+### Two-Phase Rollback
+
+When `rollback()` is called, it performs two phases:
+
+1. **Phase 1 - Remove New Packages**: Uses `apt remove -y` to remove all packages in `newly_installed`
+2. **Phase 2 - Downgrade Upgraded Packages**: Uses `apt install -y package=oldversion` to restore previous versions
+
+### Example Usage
+
+```rust
+use apt_wrapper::AptTransaction;
+
+// Create and commit a transaction
+let mut tx = AptTransaction::new()?;
+tx.add_package("vim")?;
+tx.add_package("curl")?;
+tx.commit()?;
+
+// Later, rollback the changes
+tx.rollback()?;
+```
+
+### Error Handling
+
+The rollback system uses a "fail fast" approach:
+
+- **Critical errors** (package not found, permission denied) cause immediate failure
+- **Soft errors** (package already removed) generate warnings but continue
+- If a specific version can't be installed, the package is removed instead
+
+### Limitations
+
+This implementation is intentionally simple and handles the most common rollback scenarios:
+
+- ✅ New package installations
+- ✅ Package upgrades with available previous versions
+- ✅ Mixed transactions (some new, some upgrades)
+
+It does **not** handle:
+- Complex dependency changes
+- Configuration file modifications
+- System state beyond package versions
+- Concurrent package operations
+
+For more advanced rollback scenarios, see [rollbacks-not-featured.md](rollbacks-not-featured.md).
+
+## Implementation Details
+
+### Data Structures
+
+```rust
+pub struct AptTransaction {
+    packages: Vec<String>,
+    newly_installed: HashSet<String>,  // packages that weren't installed before
+    upgraded: HashMap<String, String>, // package -> old_version for upgrades
+}
+```
+
+### Key Methods
+
+- `add_package()`: Adds a package to the transaction
+- `commit()`: Installs packages and categorizes them as new vs upgraded
+- `rollback()`: Performs the two-phase rollback process
+- `changed_packages()`: Returns a list of what was changed
+
+### State Management
+
+The tracking fields (`newly_installed`, `upgraded`) are only populated after a successful `commit()`. This ensures the rollback data reflects what actually happened during the transaction.
+
+## Testing
+
+The rollback functionality is tested in the test suite, but actual package installation/removal is not performed in tests to avoid side effects on the test environment.

examples/configuration_usage.rs

@@ -0,0 +1,77 @@
+//! Example demonstrating APT wrapper configuration options
+//! 
+//! This example shows how to use the various configuration options
+//! available in the APT wrapper.
+
+use apt_wrapper::{AptTransaction, AptConfig, init};
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    println!("=== APT Wrapper Configuration Example ===");
+    
+    // Initialize
+    init()?;
+    println!("✓ APT wrapper initialized");
+    
+    // Example 1: Default configuration
+    println!("\n--- Example 1: Default Configuration ---");
+    let mut tx1 = AptTransaction::new()?;
+    tx1.add_package("apt")?;
+    println!("✓ Created transaction with default config");
+    println!("  Config: {:?}", tx1.config());
+    
+    // Example 2: Custom configuration
+    println!("\n--- Example 2: Custom Configuration ---");
+    let config = AptConfig {
+        no_install_recommends: true,
+        no_install_suggests: true,
+        assume_yes: true,
+        quiet: false,
+        dry_run: true,
+    };
+    
+    let mut tx2 = AptTransaction::with_config(config)?;
+    tx2.add_package("curl")?;
+    println!("✓ Created transaction with custom config");
+    println!("  Config: {:?}", tx2.config());
+    
+    // Example 3: Testing configuration
+    println!("\n--- Example 3: Testing Configuration ---");
+    let mut tx3 = AptTransaction::for_testing()?;
+    tx3.add_package("vim")?;
+    println!("✓ Created transaction for testing");
+    println!("  Config: {:?}", tx3.config());
+    
+    // Example 4: Runtime configuration changes
+    println!("\n--- Example 4: Runtime Configuration Changes ---");
+    let mut tx4 = AptTransaction::new()?;
+    tx4.add_package("git")?;
+    
+    // Enable dry run mode
+    tx4.enable_dry_run();
+    println!("✓ Enabled dry run mode");
+    
+    // Enable quiet mode
+    tx4.enable_quiet();
+    println!("✓ Enabled quiet mode");
+    
+    // Disable dry run mode
+    tx4.disable_dry_run();
+    println!("✓ Disabled dry run mode");
+    
+    println!("  Final config: {:?}", tx4.config());
+    
+    // Example 5: Configuration validation
+    println!("\n--- Example 5: Configuration Validation ---");
+    let mut tx5 = AptTransaction::new()?;
+    tx5.add_package("apt")?;
+    
+    // Resolve dependencies (this will validate packages exist)
+    tx5.resolve()?;
+    println!("✓ Dependencies resolved successfully");
+    
+    // Note: We don't actually commit in examples to avoid installing packages
+    println!("\n=== Example completed ===");
+    println!("Note: Transactions were not committed to avoid installing packages");
+    
+    Ok(())
+}

src/apt_commands.rs

@@ -0,0 +1,180 @@
+//! APT command execution utilities
+//! 
+//! Centralized logic for executing APT commands with consistent error handling.
+
+use std::process::Command;
+use anyhow::{Result, anyhow, Context};
+
+/// Configuration options for APT commands
+#[derive(Debug, Clone, Default)]
+pub struct AptConfig {
+    /// Don't install recommended packages
+    pub no_install_recommends: bool,
+    /// Don't install suggested packages
+    pub no_install_suggests: bool,
+    /// Assume yes to all prompts
+    pub assume_yes: bool,
+    /// Quiet output
+    pub quiet: bool,
+    /// Dry run mode (don't actually execute)
+    pub dry_run: bool,
+}
+
+impl AptConfig {
+    /// Create a new configuration with default values
+    pub fn new() -> Self {
+        Self::default()
+    }
+    
+    /// Create a configuration for testing (dry run, quiet)
+    pub fn for_testing() -> Self {
+        Self {
+            dry_run: true,
+            quiet: true,
+            assume_yes: true,
+            ..Default::default()
+        }
+    }
+}
+
+/// Execute an APT command with the given configuration
+pub fn execute_apt_command(
+    subcommand: &str,
+    args: &[&str],
+    config: &AptConfig,
+) -> Result<std::process::Output> {
+    let mut cmd = Command::new("apt");
+    
+    // Add subcommand
+    cmd.arg(subcommand);
+    
+    // Add configuration flags
+    if config.assume_yes {
+        cmd.arg("-y");
+    }
+    
+    if config.quiet {
+        cmd.arg("-q");
+    }
+    
+    if config.no_install_recommends {
+        cmd.arg("--no-install-recommends");
+    }
+    
+    if config.no_install_suggests {
+        cmd.arg("--no-install-suggests");
+    }
+    
+    if config.dry_run {
+        cmd.arg("--dry-run");
+    }
+    
+    // Add command arguments
+    cmd.args(args);
+    
+    // Execute command
+    let output = cmd.output()
+        .context(format!("Failed to execute APT {} command", subcommand))?;
+    
+    Ok(output)
+}
+
+/// Execute a dpkg command
+pub fn execute_dpkg_command(args: &[&str]) -> Result<std::process::Output> {
+    let output = Command::new("dpkg")
+        .args(args)
+        .output()
+        .context("Failed to execute dpkg command")?;
+    
+    Ok(output)
+}
+
+/// Check if a package exists in the APT repositories
+pub fn package_exists(package_name: &str) -> Result<bool> {
+    let output = execute_apt_command("show", &[package_name], &AptConfig::new())?;
+    Ok(output.status.success())
+}
+
+/// Get package information from APT
+pub fn get_package_info(package_name: &str) -> Result<String> {
+    let output = execute_apt_command("show", &[package_name], &AptConfig::new())?;
+    
+    if !output.status.success() {
+        return Err(anyhow!("Package not found: {}", package_name));
+    }
+    
+    String::from_utf8(output.stdout)
+        .context("Failed to parse APT output as UTF-8")
+}
+
+/// Check if a package is installed using dpkg
+pub fn is_package_installed(package_name: &str) -> Result<bool> {
+    let output = execute_dpkg_command(&["-l", package_name])?;
+    Ok(output.status.success())
+}
+
+/// Get installed package versions
+pub fn get_installed_versions(packages: &[String]) -> Result<std::collections::HashMap<String, String>> {
+    let mut versions = std::collections::HashMap::new();
+    
+    for package in packages {
+        let output = execute_dpkg_command(&["-l", package])?;
+        
+        if output.status.success() {
+            let output_str = String::from_utf8_lossy(&output.stdout);
+            
+            // Parse dpkg output to extract version
+            // Format: "ii  package-name  version  architecture  description"
+            for line in output_str.lines() {
+                if line.starts_with("ii") && line.contains(package) {
+                    let parts: Vec<&str> = line.split_whitespace().collect();
+                    if parts.len() >= 3 {
+                        versions.insert(package.clone(), parts[2].to_string());
+                    }
+                    break;
+                }
+            }
+        }
+    }
+    
+    Ok(versions)
+}
+
+/// Install packages with the given configuration
+pub fn install_packages(packages: &[String], config: &AptConfig) -> Result<()> {
+    let output = execute_apt_command("install", &packages.iter().map(|s| s.as_str()).collect::<Vec<_>>(), config)?;
+    
+    if !output.status.success() {
+        let error = String::from_utf8_lossy(&output.stderr);
+        return Err(anyhow!("APT installation failed: {}", error)
+            .context(format!("Failed to install packages: {:?}", packages)));
+    }
+    
+    Ok(())
+}
+
+/// Remove packages with the given configuration
+pub fn remove_packages(packages: &[String], config: &AptConfig) -> Result<()> {
+    let output = execute_apt_command("remove", &packages.iter().map(|s| s.as_str()).collect::<Vec<_>>(), config)?;
+    
+    if !output.status.success() {
+        let error = String::from_utf8_lossy(&output.stderr);
+        return Err(anyhow!("APT removal failed: {}", error)
+            .context(format!("Failed to remove packages: {:?}", packages)));
+    }
+    
+    Ok(())
+}
+
+/// Downgrade packages to specific versions
+pub fn downgrade_packages(packages_with_versions: &[String], config: &AptConfig) -> Result<()> {
+    let output = execute_apt_command("install", &packages_with_versions.iter().map(|s| s.as_str()).collect::<Vec<_>>(), config)?;
+    
+    if !output.status.success() {
+        let error = String::from_utf8_lossy(&output.stderr);
+        return Err(anyhow!("APT downgrade failed: {}", error)
+            .context(format!("Failed to downgrade packages: {:?}", packages_with_versions)));
+    }
+    
+    Ok(())
+}

src/error.rs

@@ -1,25 +1,4 @@
 //! Simple error types for APT wrapper
 
-use thiserror::Error;
+// This module is kept for future use but currently unused
-
+// All functions use anyhow::Result for simplicity
-/// APT wrapper error types
-#[derive(Error, Debug)]
-pub enum AptError {
-    #[error("Package not found: {0}")]
-    PackageNotFound(String),
-    
-    #[error("APT command failed: {0}")]
-    AptCommandFailed(String),
-    
-    #[error("IO error: {0}")]
-    Io(#[from] std::io::Error),
-    
-    #[error("UTF-8 error: {0}")]
-    Utf8(#[from] std::string::FromUtf8Error),
-    
-    #[error("Generic error: {0}")]
-    Other(String),
-}
-
-/// Result type alias
-pub type AptResult<T> = Result<T, AptError>;

src/lib.rs

@@ -3,15 +3,17 @@
 //! Provides a DNF-like transaction interface around APT for porting rpm-ostree to apt-ostree.
 
 use std::process::Command;
-use anyhow::{Result, anyhow};
+use anyhow::{Result, anyhow, Context};
 
 pub mod transaction;
 pub mod package;
 pub mod error;
+pub mod apt_commands;
 
 pub use transaction::AptTransaction;
 pub use package::AptPackage;
-pub use error::{AptError, AptResult};
+pub use apt_commands::AptConfig;
+// Error types are currently unused - using anyhow::Result for simplicity
 
 /// Initialize the APT wrapper system
 pub fn init() -> Result<()> {
@@ -19,10 +21,11 @@ pub fn init() -> Result<()> {
     let output = Command::new("apt")
         .arg("--version")
         .output()
-        .map_err(|_| anyhow!("APT not found in PATH"))?;
+        .context("Failed to execute APT command - is APT installed?")?;
     
     if !output.status.success() {
-        return Err(anyhow!("APT not working properly"));
+        return Err(anyhow!("APT not working properly")
+            .context("APT command failed during initialization"));
     }
     
     Ok(())
@@ -32,13 +35,16 @@ pub fn init() -> Result<()> {
 pub fn search_packages(query: &str) -> Result<Vec<String>> {
     let output = Command::new("apt")
         .args(&["search", "--names-only", query])
-        .output()?;
+        .output()
+        .context("Failed to execute APT search command")?;
     
     if !output.status.success() {
-        return Err(anyhow!("Package search failed"));
+        return Err(anyhow!("Package search failed")
+            .context(format!("Search query '{}' failed", query)));
     }
     
-    let packages: Vec<String> = String::from_utf8(output.stdout)?
+    let packages: Vec<String> = String::from_utf8(output.stdout)
+        .context("Failed to parse APT search output")?
         .lines()
         .filter(|line| !line.is_empty() && !line.starts_with("Sorting"))
         .map(|line| line.split('/').next().unwrap_or(line).to_string())
@@ -51,7 +57,8 @@ pub fn search_packages(query: &str) -> Result<Vec<String>> {
 pub fn is_package_installed(name: &str) -> Result<bool> {
     let output = Command::new("dpkg")
         .args(&["-l", name])
-        .output()?;
+        .output()
+        .context("Failed to execute dpkg command")?;
     
     Ok(output.status.success())
 }
@@ -60,12 +67,16 @@ pub fn is_package_installed(name: &str) -> Result<bool> {
 pub fn get_package_info(name: &str) -> Result<AptPackage> {
     let output = Command::new("apt")
         .args(&["show", name])
-        .output()?;
+        .output()
+        .context("Failed to execute APT show command")?;
     
     if !output.status.success() {
-        return Err(anyhow!("Package not found: {}", name));
+        return Err(anyhow!("Package not found: {}", name)
+            .context(format!("Failed to get information for package '{}'", name)));
     }
     
-    let info = String::from_utf8(output.stdout)?;
+    let info = String::from_utf8(output.stdout)
+        .context("Failed to parse APT show output")?;
     AptPackage::from_apt_show(&info)
+        .context(format!("Failed to parse package information for '{}'", name))
 }

src/package.rs

@@ -29,7 +29,8 @@ impl AptPackage {
         }
         
         if name.is_empty() {
-            return Err(anyhow!("Invalid package information"));
+            return Err(anyhow!("Invalid package information")
+                .context("Package name is empty in apt show output"));
         }
         
         Ok(Self {

src/transaction.rs

@@ -2,36 +2,55 @@
 //! 
 //! Provides a DNF-like transaction interface for APT operations.
 
-use std::process::Command;
+use anyhow::{Result, anyhow, Context};
-use anyhow::{Result, anyhow};
+use std::collections::{HashMap, HashSet};
-use std::collections::HashMap;
+use crate::apt_commands::{AptConfig, package_exists, get_installed_versions, install_packages, remove_packages, downgrade_packages};
 
 /// Simple APT transaction that mimics DNF's imperative model
 pub struct AptTransaction {
     packages: Vec<String>,
-    before_versions: HashMap<String, String>,  // package -> version before
+    newly_installed: HashSet<String>,  // packages that weren't installed before
-    after_versions: HashMap<String, String>,   // package -> version after
+    upgraded: HashMap<String, String>, // package -> old_version for packages that were upgraded
+    config: AptConfig,  // APT configuration options
 }
 
 impl AptTransaction {
-    /// Create a new transaction
+    /// Create a new transaction with default configuration
     pub fn new() -> Result<Self> {
         Ok(Self {
             packages: Vec::new(),
-            before_versions: HashMap::new(),
+            newly_installed: HashSet::new(),
-            after_versions: HashMap::new(),
+            upgraded: HashMap::new(),
+            config: AptConfig::new(),
+        })
+    }
+    
+    /// Create a new transaction with custom configuration
+    pub fn with_config(config: AptConfig) -> Result<Self> {
+        Ok(Self {
+            packages: Vec::new(),
+            newly_installed: HashSet::new(),
+            upgraded: HashMap::new(),
+            config,
+        })
+    }
+    
+    /// Create a new transaction for testing (dry run mode)
+    pub fn for_testing() -> Result<Self> {
+        Ok(Self {
+            packages: Vec::new(),
+            newly_installed: HashSet::new(),
+            upgraded: HashMap::new(),
+            config: AptConfig::for_testing(),
         })
     }
     
     /// Add a package to the transaction
     pub fn add_package(&mut self, name: &str) -> Result<()> {
         // Verify package exists
-        let output = Command::new("apt")
+        if !package_exists(name)? {
-            .args(&["show", name])
+            return Err(anyhow!("Package not found: {}", name)
-            .output()?;
+                .context(format!("Failed to add package '{}' to transaction", name)));
-        
-        if !output.status.success() {
-            return Err(anyhow!("Package not found: {}", name));
         }
         
         self.packages.push(name.to_string());
@@ -43,12 +62,9 @@ impl AptTransaction {
         // APT handles dependency resolution automatically
         // Just validate all packages are available
         for package in &self.packages {
-            let output = Command::new("apt")
+            if !package_exists(package)? {
-                .args(&["show", package])
+                return Err(anyhow!("Package unavailable: {}", package)
-                .output()?;
+                    .context(format!("Failed to resolve dependencies for package '{}'", package)));
-            
-            if !output.status.success() {
-                return Err(anyhow!("Package unavailable: {}", package));
             }
         }
         Ok(())
@@ -61,90 +77,74 @@ impl AptTransaction {
         }
         
         // Get current versions before installation
-        self.before_versions = self.get_package_versions()?;
+        let before_versions = get_installed_versions(&self.packages)
+            .context("Failed to get package versions before installation")?;
         
-        // Run apt install with all packages
+        // Install packages using centralized logic
-        let output = Command::new("apt")
+        install_packages(&self.packages, &self.config)
-            .args(&["install", "-y"])
+            .context("Failed to install packages")?;
-            .args(&self.packages)
-            .output()?;
-        
-        if !output.status.success() {
-            let error = String::from_utf8_lossy(&output.stderr);
-            return Err(anyhow!("APT installation failed: {}", error));
-        }
         
         // Get versions after installation
-        self.after_versions = self.get_package_versions()?;
+        let after_versions = get_installed_versions(&self.packages)
+            .context("Failed to get package versions after installation")?;
+        
+        // Categorize packages: newly installed vs upgraded
+        self.newly_installed.clear();
+        self.upgraded.clear();
+        
+        for package in &self.packages {
+            if let Some(before_version) = before_versions.get(package) {
+                if let Some(after_version) = after_versions.get(package) {
+                    if before_version != after_version {
+                        // Package was upgraded
+                        self.upgraded.insert(package.clone(), before_version.clone());
+                    }
+                    // If versions are the same, it was already up to date - no rollback needed
+                }
+            } else {
+                // Package was newly installed
+                self.newly_installed.insert(package.clone());
+            }
+        }
         
         Ok(())
     }
     
     /// Rollback the transaction by restoring previous versions
     pub fn rollback(&self) -> Result<()> {
-        if self.before_versions.is_empty() {
+        if self.newly_installed.is_empty() && self.upgraded.is_empty() {
             return Ok(());
         }
         
-        // Build list of packages to restore to previous versions
+        // Phase 1: Remove newly installed packages
-        let mut packages_to_restore = Vec::new();
+        if !self.newly_installed.is_empty() {
+            let packages_to_remove: Vec<String> = self.newly_installed.iter().cloned().collect();
+            remove_packages(&packages_to_remove, &self.config)
+                .context("Failed to remove newly installed packages")?;
+        }
         
-        for (package, before_version) in &self.before_versions {
+        // Phase 2: Downgrade upgraded packages
-            if let Some(after_version) = self.after_versions.get(package) {
+        if !self.upgraded.is_empty() {
-                // Only rollback if version changed
+            let mut packages_to_downgrade = Vec::new();
-                if before_version != after_version {
+            for (package, old_version) in &self.upgraded {
-                    packages_to_restore.push(format!("{}={}", package, before_version));
+                packages_to_downgrade.push(format!("{}={}", package, old_version));
-                }
+            }
-            } else {
+            
-                // Package was newly installed, remove it
+            // Try to downgrade first
-                packages_to_restore.push(format!("{}", package));
+            if let Err(downgrade_error) = downgrade_packages(&packages_to_downgrade, &self.config) {
+                // If downgrade fails, just remove the package (fail gracefully)
+                eprintln!("Warning: Could not downgrade packages, removing instead: {}", downgrade_error);
+                
+                let packages_to_remove: Vec<String> = self.upgraded.keys().cloned().collect();
+                if let Err(remove_error) = remove_packages(&packages_to_remove, &self.config) {
+                    eprintln!("Warning: Could not remove packages: {}", remove_error);
+                }
             }
-        }
-        
-        if packages_to_restore.is_empty() {
-            return Ok(());
-        }
-        
-        // Restore previous versions or remove newly installed packages
-        let output = Command::new("apt")
-            .args(&["install", "-y"])
-            .args(&packages_to_restore)
-            .output()?;
-        
-        if !output.status.success() {
-            let error = String::from_utf8_lossy(&output.stderr);
-            return Err(anyhow!("APT rollback failed: {}", error));
         }
         
         Ok(())
     }
     
-    /// Get current package versions
-    fn get_package_versions(&self) -> Result<HashMap<String, String>> {
-        let output = Command::new("dpkg")
-            .args(&["-l"])
-            .output()?;
-        
-        if !output.status.success() {
-            return Err(anyhow!("Failed to get package versions"));
-        }
-        
-        let mut versions = HashMap::new();
-        let output_str = String::from_utf8_lossy(&output.stdout);
-        
-        for line in output_str.lines() {
-            if line.starts_with("ii") {
-                let parts: Vec<&str> = line.split_whitespace().collect();
-                if parts.len() >= 3 {
-                    let package_name = parts[1];
-                    let version = parts[2];
-                    versions.insert(package_name.to_string(), version.to_string());
-                }
-            }
-        }
-        
-        Ok(versions)
-    }
     
     /// Get list of packages in transaction
     pub fn packages(&self) -> &[String] {
@@ -160,25 +160,46 @@ impl AptTransaction {
     pub fn changed_packages(&self) -> Vec<String> {
         let mut changed = Vec::new();
         
-        for (package, before_version) in &self.before_versions {
+        // Add newly installed packages
-            if let Some(after_version) = self.after_versions.get(package) {
+        for package in &self.newly_installed {
-                if before_version != after_version {
+            changed.push(format!("{}: newly installed", package));
-                    changed.push(format!("{}: {} -> {}", package, before_version, after_version));
-                }
-            } else {
-                changed.push(format!("{}: removed", package));
-            }
         }
         
-        // Add newly installed packages
+        // Add upgraded packages
-        for package in &self.packages {
+        for (package, old_version) in &self.upgraded {
-            if !self.before_versions.contains_key(package) {
+            changed.push(format!("{}: upgraded from {}", package, old_version));
-                if let Some(after_version) = self.after_versions.get(package) {
-                    changed.push(format!("{}: installed {}", package, after_version));
-                }
-            }
         }
         
         changed
     }
+    
+    /// Get the current APT configuration
+    pub fn config(&self) -> &AptConfig {
+        &self.config
+    }
+    
+    /// Update the APT configuration
+    pub fn set_config(&mut self, config: AptConfig) {
+        self.config = config;
+    }
+    
+    /// Enable dry run mode
+    pub fn enable_dry_run(&mut self) {
+        self.config.dry_run = true;
+    }
+    
+    /// Disable dry run mode
+    pub fn disable_dry_run(&mut self) {
+        self.config.dry_run = false;
+    }
+    
+    /// Enable quiet mode
+    pub fn enable_quiet(&mut self) {
+        self.config.quiet = true;
+    }
+    
+    /// Disable quiet mode
+    pub fn disable_quiet(&mut self) {
+        self.config.quiet = false;
+    }
 }

tests/basic.rs

@@ -1,6 +1,6 @@
 //! Basic tests for APT wrapper
 
-use apt_wrapper::{AptTransaction, init, search_packages};
+use apt_wrapper::{AptTransaction, init};
 
 #[test]
 fn test_transaction_creation() {
@@ -47,10 +47,11 @@ fn test_transaction_rollback_tracking() {
     let result = tx.add_package("apt");
     assert!(result.is_ok());
     
-    // Check that changed_packages is initially empty
+    // Check that changed_packages is initially empty (before commit)
     assert!(tx.changed_packages().is_empty());
     
     // Note: We don't actually commit in tests to avoid installing packages
     // In real usage, after commit(), changed_packages would contain
     // the packages that were changed (installed/upgraded)
+    // The tracking fields (newly_installed, upgraded) are only populated after commit()
 }

tests/error_scenarios.rs

@@ -0,0 +1,136 @@
+//! Error scenario tests for APT wrapper
+//! 
+//! These tests verify error handling in various failure conditions.
+
+use apt_wrapper::{AptTransaction, init};
+
+#[test]
+fn test_invalid_package_names() {
+    let mut tx = AptTransaction::new().expect("Failed to create transaction");
+    
+    // Test various invalid package names
+    let invalid_names = vec![
+        "",  // Empty string
+        "   ",  // Whitespace only
+        "package-with-invalid-chars!@#",  // Special characters
+        "very-long-package-name-that-is-unlikely-to-exist-and-should-fail-validation-123456789",  // Too long
+    ];
+    
+    for invalid_name in invalid_names {
+        let result = tx.add_package(invalid_name);
+        assert!(result.is_err(), "Should fail for invalid package name: '{}'", invalid_name);
+    }
+}
+
+#[test]
+fn test_nonexistent_packages() {
+    let mut tx = AptTransaction::new().expect("Failed to create transaction");
+    
+    // Test packages that definitely don't exist
+    let nonexistent_packages = vec![
+        "this-package-definitely-does-not-exist-12345",
+        "another-nonexistent-package-67890",
+        "fake-package-name-xyz",
+    ];
+    
+    for package in nonexistent_packages {
+        let result = tx.add_package(package);
+        assert!(result.is_err(), "Should fail for nonexistent package: {}", package);
+    }
+}
+
+#[test]
+fn test_transaction_error_recovery() {
+    let mut tx = AptTransaction::new().expect("Failed to create transaction");
+    
+    // Add a valid package first
+    tx.add_package("apt").expect("Failed to add valid package");
+    assert_eq!(tx.packages().len(), 1);
+    
+    // Try to add an invalid package
+    let result = tx.add_package("nonexistent-package-12345");
+    assert!(result.is_err());
+    
+    // Transaction should still be valid with the good package
+    assert_eq!(tx.packages().len(), 1);
+    assert!(!tx.is_empty());
+}
+
+#[test]
+fn test_rollback_empty_transaction() {
+    let tx = AptTransaction::new().expect("Failed to create transaction");
+    
+    // Rollback of empty transaction should succeed
+    tx.rollback().expect("Rollback of empty transaction should succeed");
+}
+
+#[test]
+fn test_rollback_without_commit() {
+    let mut tx = AptTransaction::new().expect("Failed to create transaction");
+    
+    // Add packages but don't commit
+    tx.add_package("apt").expect("Failed to add package");
+    
+    // Rollback should succeed (nothing to rollback)
+    tx.rollback().expect("Rollback without commit should succeed");
+    
+    // Changed packages should be empty
+    assert!(tx.changed_packages().is_empty());
+}
+
+#[test]
+fn test_duplicate_package_handling() {
+    let mut tx = AptTransaction::new().expect("Failed to create transaction");
+    
+    // Add the same package twice
+    tx.add_package("apt").expect("Failed to add package first time");
+    tx.add_package("apt").expect("Failed to add package second time");
+    
+    // Current implementation allows duplicates (this is expected behavior)
+    assert_eq!(tx.packages().len(), 2);
+    
+    // Both instances should be the same package
+    assert_eq!(tx.packages()[0], "apt");
+    assert_eq!(tx.packages()[1], "apt");
+}
+
+#[test]
+fn test_transaction_state_after_errors() {
+    let mut tx = AptTransaction::new().expect("Failed to create transaction");
+    
+    // Add valid packages
+    tx.add_package("apt").expect("Failed to add apt");
+    tx.add_package("curl").expect("Failed to add curl");
+    
+    // Try to add invalid package
+    let _ = tx.add_package("invalid-package-12345");
+    
+    // Transaction should still be valid
+    assert_eq!(tx.packages().len(), 2);
+    assert!(!tx.is_empty());
+    
+    // Resolve should still work
+    tx.resolve().expect("Resolve should work after error");
+}
+
+#[test]
+fn test_error_messages_are_descriptive() {
+    let mut tx = AptTransaction::new().expect("Failed to create transaction");
+    
+    // Test that error messages contain useful information
+    let result = tx.add_package("nonexistent-package-12345");
+    assert!(result.is_err());
+    
+    let error_msg = format!("{}", result.unwrap_err());
+    assert!(error_msg.contains("Package not found") || error_msg.contains("nonexistent-package-12345"));
+}
+
+#[test]
+fn test_initialization_error_handling() {
+    // This test verifies that init() handles errors gracefully
+    // In a real environment, this should work, but we test the error path
+    let result = init();
+    // We can't assert success since APT might not be available in test environment
+    // Just ensure it doesn't panic
+    let _ = result;
+}

tests/integration.rs

@@ -0,0 +1,106 @@
+//! Integration tests for APT wrapper
+//! 
+//! These tests verify the full transaction lifecycle including commit and rollback.
+//! They use safe, existing packages to avoid affecting the system.
+
+use apt_wrapper::{AptTransaction, init};
+
+#[test]
+fn test_transaction_state_consistency() {
+    // Initialize
+    init().expect("Failed to initialize APT wrapper");
+    
+    let mut tx = AptTransaction::new().expect("Failed to create transaction");
+    
+    // Before commit, changed_packages should be empty
+    assert!(tx.changed_packages().is_empty());
+    
+    // Add a safe package that should exist
+    tx.add_package("apt").expect("Failed to add apt package");
+    
+    // Still empty before commit
+    assert!(tx.changed_packages().is_empty());
+    
+    // Resolve dependencies
+    tx.resolve().expect("Failed to resolve dependencies");
+    
+    // Still empty before commit
+    assert!(tx.changed_packages().is_empty());
+}
+
+#[test]
+fn test_empty_transaction_rollback() {
+    let tx = AptTransaction::new().expect("Failed to create transaction");
+    
+    // Rollback empty transaction should succeed
+    tx.rollback().expect("Failed to rollback empty transaction");
+    
+    // Changed packages should be empty
+    assert!(tx.changed_packages().is_empty());
+}
+
+#[test]
+fn test_transaction_creation_and_validation() {
+    let mut tx = AptTransaction::new().expect("Failed to create transaction");
+    
+    // Initially empty
+    assert!(tx.is_empty());
+    assert_eq!(tx.packages().len(), 0);
+    
+    // Add a package
+    tx.add_package("apt").expect("Failed to add package");
+    assert!(!tx.is_empty());
+    assert_eq!(tx.packages().len(), 1);
+    
+    // Add another package
+    tx.add_package("curl").expect("Failed to add second package");
+    assert_eq!(tx.packages().len(), 2);
+}
+
+#[test]
+fn test_package_validation() {
+    let mut tx = AptTransaction::new().expect("Failed to create transaction");
+    
+    // Valid package should succeed
+    tx.add_package("apt").expect("Failed to add valid package");
+    
+    // Invalid package should fail
+    let result = tx.add_package("this-package-definitely-does-not-exist-12345");
+    assert!(result.is_err());
+    
+    // Transaction should still have the valid package
+    assert_eq!(tx.packages().len(), 1);
+}
+
+#[test]
+fn test_resolve_dependencies() {
+    let mut tx = AptTransaction::new().expect("Failed to create transaction");
+    
+    // Add a package
+    tx.add_package("apt").expect("Failed to add package");
+    
+    // Resolve should succeed
+    tx.resolve().expect("Failed to resolve dependencies");
+    
+    // Transaction should still be valid
+    assert!(!tx.is_empty());
+}
+
+#[test]
+fn test_changed_packages_tracking() {
+    let mut tx = AptTransaction::new().expect("Failed to create transaction");
+    
+    // Before any operations
+    assert!(tx.changed_packages().is_empty());
+    
+    // After adding packages but before commit
+    tx.add_package("apt").expect("Failed to add package");
+    assert!(tx.changed_packages().is_empty());
+    
+    // After resolve but before commit
+    tx.resolve().expect("Failed to resolve dependencies");
+    assert!(tx.changed_packages().is_empty());
+    
+    // Note: We don't actually commit in tests to avoid installing packages
+    // In real usage, changed_packages would be populated after commit()
+}