dependencies.py: introduce unit testing for graph_reverse_depends

This commit introduces a new file with a basic unit test for the
graph_reverse_depends method on the Dependencies class.

Only 1 test exists right now, but various setup code and the general
pattern of the tests are valuable for creating more advanced tests,
and more tests for the Dependencies class in general.

Pytest is used to run all of the functions in the file that start with
test_, and a monkeypatch object is passed into test cases and allows
us to mock out methods on the Dependencies class, specifically the
"environment" method, which is used to query for packages variables
like DEPEND and RDEPEND. We are able to test against a small fake
denendency graph by patching the method!

Signed-off-by: John Turner <jturner.usa@gmail.com>
Signed-off-by: Sam James <sam@gentoo.org>

1 files changed, 71 insertions, 0 deletions

diff --git a/pym/gentoolkit/test/test_dependencies.py b/pym/gentoolkit/test/test_dependencies.py
new file mode 100644
index 0000000..48e9507
--- /dev/null
+++ b/pym/gentoolkit/test/test_dependencies.py
@@ -0,0 +1,71 @@
+import portage
+from typing import List, Dict, Optional
+from pytest import MonkeyPatch
+from gentoolkit.dependencies import Dependencies
+
+
+def is_cp_in_cpv(cp: str, cpv: str) -> bool:
+    other_cp, _, _ = portage.pkgsplit(cpv)
+    return cp == other_cp
+
+
+def environment(
+    self: Dependencies,
+    env_vars: List[str],
+    fake_depends: Dict[str, Optional[Dict[str, str]]],
+    fake_pkgs: List[str],
+) -> List[str]:
+    metadata = None
+    for pkg in fake_pkgs:
+        if is_cp_in_cpv(self.cp, pkg):
+            if (metadata := fake_depends[pkg]) is not None:
+                break
+    else:
+        return [""]
+    results = list()
+    for env_var in env_vars:
+        try:
+            value = metadata[env_var]
+        except KeyError:
+            value = ""
+        results.append(value)
+    return results
+
+
+def test_basic_revdeps(monkeypatch: MonkeyPatch) -> None:
+    fake_depends = {
+        "app-misc/root-1.0": None,
+        "app-misc/a-1.0": {"DEPEND": "app-misc/root"},
+        "app-misc/b-1.0": {"DEPEND": "app-misc/a"},
+        "app-misc/c-1.0": {"DEPEND": "app-misc/b"},
+        "app-misc/d-1.0": None,
+    }
+    fake_pkgs = list(fake_depends.keys())
+
+    def e(self, env_vars):
+        return environment(self, env_vars, fake_depends, fake_pkgs)
+
+    monkeypatch.setattr(Dependencies, "environment", e)
+
+    # confirm that monkeypatch is working as expected
+    assert Dependencies("app-misc/root").environment(["DEPEND"]) == [""]
+    assert Dependencies("app-misc/a").environment(["DEPEND"]) == ["app-misc/root"]
+    assert Dependencies("app-misc/b").environment(["DEPEND"]) == ["app-misc/a"]
+    assert Dependencies("app-misc/c").environment(["DEPEND"]) == ["app-misc/b"]
+    assert Dependencies("app-misc/d").environment(["DEPEND"]) == [""]
+
+    assert sorted(
+        pkg.cpv
+        for pkg in Dependencies("app-misc/root").graph_reverse_depends(pkgset=fake_pkgs)
+    ) == ["app-misc/a-1.0"]
+
+    assert sorted(
+        pkg.cpv
+        for pkg in Dependencies("app-misc/root").graph_reverse_depends(
+            pkgset=fake_pkgs, only_direct=False
+        )
+    ) == [
+        "app-misc/a-1.0",
+        "app-misc/b-1.0",
+        "app-misc/c-1.0",
+    ]