Add tests

Signed-off-by: Pavel Kulyov <[email protected]>

tests/test_topsort.py

@@ -0,0 +1,81 @@
+"""Unit tests for pytopsort module."""
+
+import pytest
+
+from pytopsort import topsort
+
+
+def test_topsort():
+    """This recipe contains no cycles and can be sorted."""
+
+    # fmt: off
+    recipe = [{
+        "action": "spread peanut butter on bread",
+        "after": ["slice bread"],
+    }, {
+        "action": "slice bread",
+        "after": [],
+    }, {
+        "action": "eat the delicious breakfast!",
+        "after": ["spread jam on top", "make a cup of coffee"],
+    }, {
+        "action": "make a cup of coffee",
+        "after": [],
+    }, {
+        "action": "spread jam on top",
+        "after": ["spread peanut butter on bread"],
+    }]
+    # fmt: on
+
+    recipe = topsort(
+        recipe, deptest=lambda self, other: self["action"] in other["after"],
+    )
+
+    # fmt: off
+    assert list(recipe) == [{
+        "action": "make a cup of coffee",
+        "after": [],
+    }, {
+        "action": "slice bread",
+        "after": [],
+    }, {
+        "action": "spread peanut butter on bread",
+        "after": ["slice bread"],
+    }, {
+        "action": "spread jam on top",
+        "after": ["spread peanut butter on bread"],
+    }, {
+        "action": "eat the delicious breakfast!",
+        "after": ["spread jam on top", "make a cup of coffee"],
+    }]
+    # fmt: on
+
+
+def test_cycles():
+    """This recipe contains a cycle (two actions depend on each other)."""
+
+    # fmt: off
+    recipe = [{
+        "action": "spread peanut butter on bread",
+        "after": ["slice bread"],
+    }, {
+        "action": "slice bread",
+        "after": ["spread peanut butter on bread"],
+    }, {
+        "action": "eat the delicious breakfast!",
+        "after": ["spread jam on top", "make a cup of coffee"],
+    }, {
+        "action": "make a cup of coffee",
+        "after": [],
+    }, {
+        "action": "spread jam on top",
+        "after": ["spread peanut butter on bread"],
+    }]
+    # fmt: on
+
+    with pytest.raises(ValueError) as exc:
+        recipe = topsort(
+            recipe, deptest=lambda self, other: self["action"] in other["after"],
+        )
+
+    assert str(exc.value) == "Dependency graph has a cycle"