diff --git a/test/initmain.c b/test/initmain.c
index edc77ef7..1d6878fa 100644
--- a/test/initmain.c
+++ b/test/initmain.c
@@ -31,7 +31,8 @@ testingTestBefore(Init)
 	if (ret != 0)
 		testingTErrorf(t, "uiInit() with non-NULL options succeeded with return value %d; expected failure", err);
 	if (strcmp(err.Message, errInvalidOptions) != 0)
-		testingTErrorf(t, "uiInit() with non-NULL options returned bad error message: got %s, want %s", err.Message, errInvalidOptions);
+		diff(t, "uiInit() with non-NULL options returned bad error message", "%s",
+			err.Message, errInvalidOptions);
 
 	memset(&err, 0, sizeof (uiInitError));
 	err.Size = sizeof (uiInitError);
@@ -45,7 +46,8 @@ testingTestBefore(Init)
 	if (ret != 0)
 		testingTErrorf(t, "uiInit() after a previous successful call succeeded with return value %d; expected failure", ret);
 	if (strcmp(err.Message, errAlreadyInitialized) != 0)
-		testingTErrorf(t, "uiInit() after a previous successful call returned bad error message: got %s, want %s", err.Message, errAlreadyInitialized);
+		diff(t, "uiInit() after a previous successful call returned bad error message", "%s",
+			err.Message, errAlreadyInitialized);
 }
 
 struct testParams {
@@ -70,7 +72,8 @@ testingTest(QueueMain)
 	uiQueueMain(queued, &p);
 	timeout_uiMain(t, 5 * timerSecond);
 	if (p.flag != 1)
-		testingTErrorf(t, "uiQueueMain() didn't set flag properly: got %d, want 1", p.flag);
+		diff(t, "uiQueueMain() didn't set flag properly", "%d",
+			p.flag, 1);
 }
 
 #define queueOp(name, expr) \
@@ -118,10 +121,14 @@ static void checkOrder(testingT *t, uint32_t flag)
 		return;
 	for (i = 1; i < 6; i++)
 		if (flag == orders[i].result) {
-			testingTErrorf(t, "got %" PRIu32 " (%s), want %" PRIu32 " (%s)", flag, orders[i].order, orders[0].result, orders[0].order);
+			diff2(t, "wrong order", "%" PRIu32 " (%s)",
+				flag, orders[i].order,
+				orders[0].result, orders[0].order);
 			return;
 		}
-	testingTErrorf(t, "got %" PRIu32 " (unknown order), want %" PRIu32 " (%s)", flag, orders[0].result, orders[0].order);
+	diff2(t, "wrong result", "%" PRIu32 " (%s)",
+		flag, "unknown order",
+		orders[0].result, orders[0].order);
 }
 	
 testingTest(QueueMain_Sequence)
@@ -160,7 +167,8 @@ testingTest(QueueMain_DifferentThread)
 	if (p.err != 0)
 		testingTErrorf(t, "error sleeping in thread to ensure a high likelihood the uiQueueMain() is run after uiMain() starts: " timerSysErrorFmt, timerSysErrorFmtArg(p.err));
 	if (p.flag != 1)
-		testingTErrorf(t, "uiQueueMain() didn't set flag properly: got %d, want 1", p.flag);
+		diff(t, "uiQueueMain() didn't set flag properly", "%d",
+			p.flag, 1);
 }
 
 static void queueOrderThread(void *data)
diff --git a/test/lib/testing.c b/test/lib/testing.c
index 539f8fa1..acd7a7dc 100644
--- a/test/lib/testing.c
+++ b/test/lib/testing.c
@@ -73,6 +73,7 @@ struct testingT {
 	jmp_buf returnNowBuf;
 	struct defer *defers;
 	int defersRun;
+	int indent;
 };
 
 #ifdef _MSC_VER
@@ -150,6 +151,63 @@ static void testsetSort(struct testset *set)
 	qsort(set->tests, set->len, sizeof (testingT), testcmp);
 }
 
+static void printIndent(int n)
+{
+	for (; n != 0; n--)
+		printf("    ");
+}
+
+static void vprintfIndented(int indent, const char *format, va_list ap)
+{
+	va_list ap2;
+	char *buf;
+	int n;
+	char *lineStart, *lineEnd;
+	int firstLine = 1;
+
+	va_copy(ap2, ap);
+	n = vsnprintf(NULL, 0, format, ap2);
+	// TODO handle n < 0 case
+	va_end(ap2);
+	buf = testingprivNewArray(char, n + 1);
+	vsnprintf(buf, n + 1, format, ap);
+
+	// strip trailing blank lines
+	while (buf[n - 1] == '\n')
+		n--;
+	buf[n] = '\0';
+
+	lineStart = buf;
+	for (;;) {
+		lineEnd = strchr(lineStart, '\n');
+		if (lineEnd == NULL)			// last line
+			break;
+		*lineEnd = '\0';
+		printIndent(indent);
+		printf("%s\n", lineStart);
+		lineStart = lineEnd + 1;
+		if (firstLine) {
+			// subsequent lines are indented twice
+			indent++;
+			firstLine = 0;
+		}
+	}
+	// print the last line
+	printIndent(indent);
+	printf("%s\n", lineStart);
+
+	testingprivFree(buf);
+}
+
+static void printfIndented(int indent, const char *format, ...)
+{
+	va_list ap;
+
+	va_start(ap, format);
+	vprintfIndented(indent, format, ap);
+	va_end(ap);
+}
+
 static void runDefers(testingT *t)
 {
 	struct defer *d;
@@ -161,7 +219,7 @@ static void runDefers(testingT *t)
 		(*(d->f))(t, d->data);
 }
 
-static void testsetRun(struct testset *set, int *anyFailed)
+static void testsetRun(struct testset *set, int indent, int *anyFailed)
 {
 	size_t i;
 	testingT *t;
@@ -171,7 +229,8 @@ static void testsetRun(struct testset *set, int *anyFailed)
 
 	t = set->tests;
 	for (i = 0; i < set->len; i++) {
-		printf("=== RUN   %s\n", t->name);
+		printfIndented(indent, "=== RUN   %s\n", t->name);
+		t->indent = indent + 1;
 		start = timerMonotonicNow();
 		if (setjmp(t->returnNowBuf) == 0)
 			(*(t->f))(t);
@@ -186,7 +245,7 @@ static void testsetRun(struct testset *set, int *anyFailed)
 			// note that failed overrides skipped
 			status = "SKIP";
 		timerDurationString(timerTimeSub(end, start), timerstr);
-		printf("--- %s: %s (%s)\n", status, t->name, timerstr);
+		printfIndented(indent, "--- %s: %s (%s)\n", status, t->name, timerstr);
 		t++;
 	}
 }
@@ -207,13 +266,13 @@ int testingMain(void)
 	testsetSort(&testsAfter);
 
 	anyFailed = 0;
-	testsetRun(&testsBefore, &anyFailed);
+	testsetRun(&testsBefore, 0, &anyFailed);
 	// TODO print a warning that we skip the next stages if a prior stage failed?
 	if (!anyFailed)
-		testsetRun(&tests, &anyFailed);
+		testsetRun(&tests, 0, &anyFailed);
 	// TODO should we unconditionally run these tests if before succeeded but the main tests failed?
 	if (!anyFailed)
-		testsetRun(&testsAfter, &anyFailed);
+		testsetRun(&testsAfter, 0, &anyFailed);
 	if (anyFailed) {
 		printf("FAIL\n");
 		return 1;
@@ -233,11 +292,22 @@ void testingprivTLogfFull(testingT *t, const char *file, long line, const char *
 
 void testingprivTLogvfFull(testingT *t, const char *file, long line, const char *format, va_list ap)
 {
+	va_list ap2;
+	char *buf;
+	int n, n2;
+
 	// TODO extract filename from file
-	printf("\t%s:%ld: ", file, line);
-	// TODO split into lines separated by \n\t\t and trimming trailing empty lines
-	vprintf(format, ap);
-	printf("\n");
+	n = snprintf(NULL, 0, "%s:%ld: ", file, line);
+	// TODO handle n < 0 case
+	va_copy(ap2, ap);
+	n2 = vsnprintf(NULL, 0, format, ap2);
+	// TODO handle n2 < 0 case
+	va_end(ap2);
+	buf = testingprivNewArray(char, n + n2 + 1);
+	snprintf(buf, n + 1, "%s:%ld: ", file, line);
+	vsnprintf(buf + n, n2 + 1, format, ap);
+	printfIndented(t->indent, "%s", buf);
+	testingprivFree(buf);
 }
 
 void testingTFail(testingT *t)
diff --git a/test/test.h b/test/test.h
index ff476012..9723c3f8 100644
--- a/test/test.h
+++ b/test/test.h
@@ -3,6 +3,11 @@
 #include "lib/testing.h"
 #include "lib/timer.h"
 
+#define diff(t, clause, fmt, got, want) testingTErrorf(t, "%s:\ngot  " fmt "\nwant " fmt, clause, got, want)
+#define diff2(t, clause, fmts, got1, got2, want1, want2) testingTErrorf(t, "%s:\ngot  " fmts "\nwant " fmts, clause, got1, got2, want1, want2)
+#define diffFatal(t, clause, fmt, got, want) testingTFatalf(t, "%s:\ngot  " fmt "\nwant " fmt, clause, got, want)
+#define diff2Fatal(t, clause, fmts, got1, got2, want1, want2) testingTFatalf(t, "%s:\ngot  " fmts "\nwant " fmts, clause, got1, got2, want1, want2)
+
 // main.c
 extern void timeoutMain(void *data);
 #define timeout_uiMain(t, d) { \