replace jest with ava

node_modules/concordance/lib/getCtor.js

@@ -0,0 +1,43 @@
+'use strict'
+
+const hop = Object.prototype.hasOwnProperty
+
+function getCtor (stringTag, value) {
+  if (value.constructor) {
+    const name = value.constructor.name
+    return typeof name === 'string' && name !== ''
+      ? name
+      : null
+  }
+
+  if (value.constructor === undefined) {
+    if (stringTag !== 'Object' || value instanceof Object) return null
+
+    // Values without a constructor, that do not inherit from `Object`, but are
+    // tagged as objects, may come from `Object.create(null)`. Or they can come
+    // from a different realm, e.g.:
+    //
+    // ```
+    // require('vm').runInNewContext(`
+    //   const Foo = function () {}
+    //   Foo.prototype.constructor = undefined
+    //   return new Foo()
+    // `)
+    // ```
+    //
+    // Treat such objects as if they came from `Object.create(null)` (in the
+    // current realm) only if they do not have inherited properties. This allows
+    // these objects to be compared with object literals.
+    //
+    // This means `Object.create(null)` is not differentiated from `{}`.
+
+    // Using `const` prevents Crankshaft optimizations
+    for (var p in value) { // eslint-disable-line no-var
+      if (!hop.call(value, p)) return null
+    }
+    return stringTag
+  }
+
+  return null
+}
+module.exports = getCtor