subsys/testsuite: Shorten the assertion messages

At present these can be very long since they include the full path of
the filename with the error.

    Assertion failed at /home/sglass/cosarm/zephry/zephyrproject/
	zephyr/tests/drivers/flash_simulator/src/main.c:102:
	test_write_read: (0 not equal to rc)

Reduce the length by omitting the current directory (where the tests
are being run) from the output:

    Assertion failed at tests/drivers/flash_simulator/src/main.c:102:
	test_write_read: (0 not equal to rc)

This improves usability for people running tests locally.

Signed-off-by: Simon Glass <sjg@chromium.org>

subsys/testsuite/ztest/include/ztest_assert.h

@@ -23,6 +23,7 @@
 extern "C" {
 #endif
 
+const char *ztest_relative_filename(const char *file);
 void ztest_test_fail(void);
 #if CONFIG_ZTEST_ASSERT_VERBOSE == 0
 
@@ -30,7 +31,7 @@ static inline void z_zassert_(bool cond, const char *file, int line)
 {
 	if (cond == false) {
 		PRINT("\n    Assertion failed at %s:%d\n",
-		      file, line);
+		      ztest_relative_filename(file), line);
 		ztest_test_fail();
 	}
 }
@@ -51,7 +52,7 @@ static inline void z_zassert(bool cond,
 
 		va_start(vargs, msg);
 		PRINT("\n    Assertion failed at %s:%d: %s: %s\n",
-		      file, line, func, default_msg);
+		      ztest_relative_filename(file), line, func, default_msg);
 		vprintk(msg, vargs);
 		printk("\n");
 		va_end(vargs);
@@ -60,7 +61,7 @@ static inline void z_zassert(bool cond,
 #if CONFIG_ZTEST_ASSERT_VERBOSE == 2
 	else {
 		PRINT("\n   Assertion succeeded at %s:%d (%s)\n",
-		      file, line, func);
+		      ztest_relative_filename(file), line, func);
 	}
 #endif
 }

subsys/testsuite/ztest/src/ztest.c

@@ -16,6 +16,10 @@
 static struct k_thread ztest_thread;
 #endif
 
+#ifdef CONFIG_ARCH_POSIX
+#include <unistd.h>
+#endif
+
 /* ZTEST_DMEM and ZTEST_BMEM are used for the application shared memory test  */
 
 ZTEST_DMEM enum {
@@ -27,6 +31,31 @@ ZTEST_DMEM enum {
 
 static ZTEST_BMEM int test_status;
 
+/**
+ * @brief Try to shorten a filename by removing the current directory
+ *
+ * This helps to reduce the very long filenames in assertion failures. It
+ * removes the current directory from the filename and returns the rest.
+ * This makes assertions a lot more readable, and sometimes they fit on one
+ * line.
+ *
+ * @param file Filename to check
+ * @returns Shortened filename, or @file if it could not be shortened
+ */
+const char *ztest_relative_filename(const char *file)
+{
+#ifdef CONFIG_ARCH_POSIX
+	const char *cwd;
+	char buf[200];
+
+	cwd = getcwd(buf, sizeof(buf));
+	if (cwd && strlen(file) > strlen(cwd) &&
+	    !strncmp(file, cwd, strlen(cwd)))
+		return file + strlen(cwd) + 1; /* move past the trailing '/' */
+#endif
+	return file;
+}
+
 static int cleanup_test(struct unit_test *test)
 {
 	int ret = TC_PASS;