test(_comp_abspath): add some unit tests

test/t/unit/Makefile.am

@@ -1,4 +1,5 @@
 EXTRA_DIST = \
+	test_unit_abspath.py \
 	test_unit_command_offset.py \
 	test_unit_count_args.py \
 	test_unit_deprecate_func.py \

test/t/unit/test_unit_abspath.py

@@ -0,0 +1,67 @@
+import pytest
+
+from conftest import assert_bash_exec
+
+
+@pytest.mark.bashcomp(
+    cmd=None, cwd="shared", ignore_env=r"^\+declare -f __tester$"
+)
+class TestUnitAbsPath:
+    @pytest.fixture
+    def functions(self, bash):
+        assert_bash_exec(
+            bash,
+            (
+                "__tester() { "
+                "local ret; "
+                '_comp_abspath "$1"; '
+                'printf %s "$ret"; '
+                "}"
+            ),
+        )
+
+    def test_non_pollution(self, bash):
+        """Test environment non-pollution, detected at teardown."""
+        assert_bash_exec(
+            bash,
+            "foo() { local ret=; _comp_abspath bar; }; foo; unset -f foo",
+            want_output=None,
+        )
+
+    def test_absolute(self, bash, functions):
+        output = assert_bash_exec(
+            bash,
+            "__tester /foo/bar",
+            want_output=True,
+            want_newline=False,
+        )
+        assert output.strip() == "/foo/bar"
+
+    def test_relative(self, bash, functions):
+        output = assert_bash_exec(
+            bash,
+            "__tester foo/bar",
+            want_output=True,
+            want_newline=False,
+        )
+        assert output.strip().endswith("/shared/foo/bar")
+
+    def test_cwd(self, bash, functions):
+        output = assert_bash_exec(
+            bash,
+            "__tester ./foo/./bar",
+            want_output=True,
+            want_newline=False,
+        )
+        assert output.strip().endswith("/shared/foo/bar")
+
+    def test_parent(self, bash, functions):
+        output = assert_bash_exec(
+            bash,
+            "__tester ../shared/foo/bar",
+            want_output=True,
+            want_newline=False,
+        )
+        assert output.strip().endswith(
+            "/shared/foo/bar"
+        ) and not output.strip().endswith("../shared/foo/bar")