Add tests and docstring for VersionConstraint

Signed-off-by: Tushar Goel <tushar.goel.dav@gmail.com>

Author: TG1999

src/univers/version_constraint.py

@@ -136,6 +136,11 @@ def is_star(self):
         return self.comparator == "*"
 
     def invert(self):
+        """
+        Return a new VersionConstraint instance with the comparator inverted.
+        For example::
+        >>> assert str(VersionConstraint(comparator=">=", version=Version("2.3")).invert()) == "<2.3"
+        """
         INVERTED_COMPARATORS = {
             ">=": "<",
             "<=": ">",

tests/test_version_constraint.py

@@ -60,3 +60,30 @@ def test_semver_comparison(version, spec, expected):
         version_class=versions.SemverVersion,
     )
     assert (version in constraint) is expected
+
+
+@pytest.mark.parametrize(
+    "original, inverted",
+    [
+        (">2.7.1", "<=2.7.1"),
+        ("!=1.1.0", "=1.1.0"),
+        ("=2.0.0", "!=2.0.0"),
+        ("<=0.9999.9999", ">0.9999.9999"),
+        (">=0.2.9", "<0.2.9"),
+        ("<1.9999.9999", ">=1.9999.9999"),
+        ("*", None),
+    ],
+)
+def test_invert_opertaion(original, inverted):
+    constraint = VersionConstraint.from_string(
+        string=original,
+        version_class=versions.SemverVersion,
+    )
+    if inverted:
+        inverted_constraint = VersionConstraint.from_string(
+            string=inverted,
+            version_class=versions.SemverVersion,
+        )
+        assert constraint.invert() == inverted_constraint
+    else:
+        assert constraint.invert() is None

tests/test_version_range.py

@@ -395,7 +395,7 @@ def test_npm_advisory_version_range_parse(test_case):
     assert str(result) == test_case["expected_vers"]
 
 
-def test_inverse():
+def test_invert():
     vers_with_equal_operator = VersionRange.from_string("vers:gem/1.0")
     assert str(vers_with_equal_operator.invert()) == "vers:gem/!=1.0"
     assert VersionRange.from_string("vers:gem/!=1.0").invert() == vers_with_equal_operator
@@ -410,3 +410,6 @@ def test_inverse():
 
     vers_with_complex_constraints = VersionRange.from_string("vers:gem/<=1.0|>=3.0|<4.0|!=5.0")
     assert str(vers_with_complex_constraints.invert()) == "vers:gem/>1.0|<3.0|>=4.0|5.0"
+
+    vers_with_star_operator = VersionRange.from_string("vers:gem/*")
+    assert vers_with_star_operator.invert() == None