diff --git a/common/opentype_test.c b/common/opentype_test.c
index 784073a8..b494527b 100644
--- a/common/opentype_test.c
+++ b/common/opentype_test.c
@@ -1,10 +1,26 @@
-xx 27 february 2018
+// 27 february 2018
 #ifndef TODO_TEST
 #error TODO this is where libui itself goes
 #endif
 
 #include <stdarg.h>
 
+#undef testingprivBadLanguageVersion
+#ifdef __cplusplus
+// TODO https://stackoverflow.com/questions/2324658/how-to-determine-the-version-of-the-c-standard-used-by-the-compiler implies this won't do with C++0x-era compilers, and https://wiki.apache.org/stdcxx/C++0xCompilerSupport doesn't talk about va_copy() so a simple version check for the C99 preprocessor may be wrong...
+// TODO what if __cplusplus is blank (maybe only in that case, since IIRC C++98 requires __cplusplus to have a value)?
+#if __cplusplus < 201103L
+#define testingprivBadLanguageVersion
+#endif
+#elif !defined(__STDC_VERSION__)
+#define testingprivBadLanguageVersion
+#elif __STDC_VERSION__ < 199901L
+#define testingprivBadLanguageVersion
+#endif
+#ifdef testingprivBadLanguageVersion
+#error sorry, TODO requires either C99 or TODO; cannot continue
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -21,13 +37,13 @@ extern "C" {
 extern int testingMain(void);
 
 typedef struct testingT testingT;
-#define testingTErrorf(t, ...) testingprivTLogFull(t, __FILE__, __LINE__, __VA_ARGS__)
-#define testingTErrorvf(t, format, ap) testingprivTLogFullv(t, __FILE__, __LINE__, format, ap)
+#define testingTErrorf(t, ...) testingprivTErrorfFull(t, __FILE__, __LINE__, __VA_ARGS__)
+#define testingTErrorvf(t, format, ap) testingprivTErrorvfFull(t, __FILE__, __LINE__, format, ap)
 
-extern void testingprivRegisterTest(const char *, void (*)(testi
-ngT *));
-extern void testingprivTLogFull(testingT *, const char *, int, const char *, ...);
-extern void testingprivTLogFullv(testingT *, const char *, int, const char *, va_list);
+// TODO should __LINE__ arguments use intmax_t or uintmax_t instead of int?
+extern void testingprivRegisterTest(const char *, void (*)(testingT *));
+extern void testingprivTErrorfFull(testingT *, const char *, int, const char *, ...);
+extern void testingprivTErrorvfFull(testingT *, const char *, int, const char *, va_list);
 
 #ifdef __cplusplus
 }
@@ -35,6 +51,7 @@ extern void testingprivTLogFullv(testingT *, const char *, int, const char *, va
 
 testingTest(Name)
 {
+	printf("in the test!\n");
 }
 
 int main(void)
@@ -60,7 +77,7 @@ void testingprivRegisterTest(const char *name, void (*f)(testingT *))
 {
 	testingT *t;
 
-	t = testingprivNew(testingT)
+	t = testingprivNew(testingT);
 	t->name = name;
 	t->f = f;
 	t->failed = 0;
@@ -76,7 +93,7 @@ int testingMain(void)
 
 	if (tests == NULL) {
 		fprintf(stderr, "warning: no tests to run\n");
-		xx imitate Go here (TODO confirm this)
+		// imitate Go here (TODO confirm this)
 		return 0;
 	}
 
@@ -100,15 +117,26 @@ int testingMain(void)
 	return 0;
 }
 
-extern void testingprivTLogFull(testingT *t, const char *file, int line, const char *format, ...)
+static void testingprivTDoLog(testingT *t, const char *file, int line, const char *format, va_list ap)
+{
+	// TODO extract filename from file
+	printf("\t%s:%d: ", file, line);
+	// TODO split into lines separated by \n\t\t and trimming trailing empty lines
+	vprintf(format, ap);
+	printf("\n");
+}
+
+void testingprivTErrorfFull(testingT *t, const char *file, int line, const char *format, ...)
 {
 	va_list ap;
 
 	va_start(ap, format);
-	testingprivTLogFullv(t, file, line, format, ap);
+	testingprivTErrorvfFull(t, file, line, format, ap);
 	va_end(ap);
 }
 
-void testingprivTLogFullv(testingT *t, const char *file, int line, const char *format, va_list ap)
+void testingprivTErrorvfFull(testingT *t, const char *file, int line, const char *format, va_list ap)
 {
+	testingprivTDoLog(t, file, line, format, ap);
+	t->failed = 1;
 }