tests: clarify test_path_startswith return value (#4508)

A pendant for #4481.

2 files changed, 41 insertions, 10 deletions

diff --git a/src/basic/path-util.c b/src/basic/path-util.c
index 0f5b20cf05..fd38f51c4c 100644
--- a/src/basic/path-util.c
+++ b/src/basic/path-util.c
@@ -354,6 +354,16 @@ char* path_startswith(const char *path, const char *prefix) {
         assert(path);
         assert(prefix);
 
+        /* Returns a pointer to the start of the first component after the parts matched by
+         * the prefix, iff
+         * - both paths are absolute or both paths are relative,
+         * and
+         * - each component in prefix in turn matches a component in path at the same position.
+         * An empty string will be returned when the prefix and path are equivalent.
+         *
+         * Returns NULL otherwise.
+         */
+
         if ((path[0] == '/') != (prefix[0] == '/'))
                 return NULL;
 
diff --git a/src/test/test-path-util.c b/src/test/test-path-util.c
index 0b10d8e25e..a6a09a0031 100644
--- a/src/test/test-path-util.c
+++ b/src/test/test-path-util.c
@@ -263,16 +263,37 @@ static void test_strv_resolve(void) {
 }
 
 static void test_path_startswith(void) {
-        assert_se(path_startswith("/foo/bar/barfoo/", "/foo"));
-        assert_se(path_startswith("/foo/bar/barfoo/", "/foo/"));
-        assert_se(path_startswith("/foo/bar/barfoo/", "/"));
-        assert_se(path_startswith("/foo/bar/barfoo/", "////"));
-        assert_se(path_startswith("/foo/bar/barfoo/", "/foo//bar/////barfoo///"));
-        assert_se(path_startswith("/foo/bar/barfoo/", "/foo/bar/barfoo////"));
-        assert_se(path_startswith("/foo/bar/barfoo/", "/foo/bar///barfoo/"));
-        assert_se(path_startswith("/foo/bar/barfoo/", "/foo////bar/barfoo/"));
-        assert_se(path_startswith("/foo/bar/barfoo/", "////foo/bar/barfoo/"));
-        assert_se(path_startswith("/foo/bar/barfoo/", "/foo/bar/barfoo"));
+        const char *p;
+
+        p = path_startswith("/foo/bar/barfoo/", "/foo");
+        assert_se(streq_ptr(p, "bar/barfoo/"));
+
+        p = path_startswith("/foo/bar/barfoo/", "/foo/");
+        assert_se(streq_ptr(p, "bar/barfoo/"));
+
+        p = path_startswith("/foo/bar/barfoo/", "/");
+        assert_se(streq_ptr(p, "foo/bar/barfoo/"));
+
+        p = path_startswith("/foo/bar/barfoo/", "////");
+        assert_se(streq_ptr(p, "foo/bar/barfoo/"));
+
+        p = path_startswith("/foo/bar/barfoo/", "/foo//bar/////barfoo///");
+        assert_se(streq_ptr(p, ""));
+
+        p = path_startswith("/foo/bar/barfoo/", "/foo/bar/barfoo////");
+        assert_se(streq_ptr(p, ""));
+
+        p = path_startswith("/foo/bar/barfoo/", "/foo/bar///barfoo/");
+        assert_se(streq_ptr(p, ""));
+
+        p = path_startswith("/foo/bar/barfoo/", "/foo////bar/barfoo/");
+        assert_se(streq_ptr(p, ""));
+
+        p = path_startswith("/foo/bar/barfoo/", "////foo/bar/barfoo/");
+        assert_se(streq_ptr(p, ""));
+
+        p = path_startswith("/foo/bar/barfoo/", "/foo/bar/barfoo");
+        assert_se(streq_ptr(p, ""));
 
         assert_se(!path_startswith("/foo/bar/barfoo/", "/foo/bar/barfooa/"));
         assert_se(!path_startswith("/foo/bar/barfoo/", "/foo/bar/barfooa"));