Refactor depsolving tests

This adds a new test for Requires(pre) and (post). The general structure
of the test now makes it easy to use the same test scenarios for
different backend.

Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>

tests/data/specs/dummy-perl.spec

@@ -0,0 +1,42 @@
+Name:           dummy-perl
+Version:        1.0.0
+Release:        1
+License:        LGPLv2
+Summary:        A dummy perl package
+Requires(pre):  dummy-perl-macros
+Requires(post): dummy-perl-utils
+
+%description
+A dummy perl package. This packages demonstrates a Requires(pre) and
+Requires(post) dependencies.
+
+%package macros
+Summary:        A dummy perl-macros package
+
+%description macros
+A dummy perl-macros package
+
+%package utils
+Summary:        A dummy perl-utils package
+
+%description utils
+A dummy perl-utils package
+
+
+%build
+echo OK
+
+
+%install
+rm -rf $RPM_BUILD_ROOT
+mkdir $RPM_BUILD_ROOT
+
+
+%files
+%files macros
+%files utils
+
+
+%changelog
+* Mon Jan 23 2017 Lubomír Sedlář <lsedlar@redhat.com> - 1.0.0-1
+- First release