diff --git a/tests/test-registrable-domain.c b/tests/test-registrable-domain.c
index e6ed954..07cc18b 100644
--- a/tests/test-registrable-domain.c
+++ b/tests/test-registrable-domain.c
@@ -41,21 +41,49 @@
 
 #define countof(a) (sizeof(a)/sizeof(*(a)))
 #define TESTDATA DATADIR"/test_psl.txt"
+
 static int
 	ok,
 	failed;
 
+static void test(const psl_ctx_t *psl, const char *domain, const char *expected_result)
+{
+	const char *result = psl_registrable_domain(psl, domain);
+
+	if ((result && expected_result && !strcmp(result, expected_result)) || (!result && !expected_result)) {
+		ok++;
+	} else {
+		failed++;
+		printf("psl_registrable_domain(%s)=%s (expected %s)\n",
+			domain, result ? result : "NULL", expected_result ? expected_result : "NULL");
+	}
+}
+
 static void test_psl(void)
 {
 	FILE *fp;
 	const psl_ctx_t *psl;
-	const char *result;
 	char buf[256], domain[128], expected_regdom[128], *p;
 
 	psl = psl_builtin();
 
 	printf("have %d suffixes and %d exceptions\n", psl_suffix_count(psl), psl_suffix_exception_count(psl));
 
+	// special check with NULL values
+	test(NULL, NULL, NULL);
+
+	// special check with NULL psl context
+	test(NULL, "www.example.com", NULL);
+
+	// special check with NULL psl context and TLD
+	test(NULL, "com", NULL);
+
+	// Norwegian with uppercase oe
+	// test(psl, "www.\303\230yer.no", "www.\303\270yer.no");
+
+	// Norwegian with lowercase oe
+	test(psl, "www.\303\270yer.no", "www.\303\270yer.no");
+
 	if ((fp = fopen(TESTDATA, "r"))) {
 		while ((fgets(buf, sizeof(buf), fp))) {
 			if (sscanf(buf, " checkPublicSuffix('%127[^']' , '%127[^']", domain, expected_regdom) != 2) {
@@ -68,19 +96,18 @@ static void test_psl(void)
 				if (isupper(*p))
 					*p = tolower(*p);
 
-			result = psl_registrable_domain(psl, domain);
-			
-			if (result == NULL) {
-				if (strcmp(expected_regdom, "null")) {
-					failed++;
-					printf("psl_registrable_domain(%s)=NULL (expected %s)\n", domain, expected_regdom);
-				} else ok++;
-			} else {
-				if (strcmp(expected_regdom, result)) {
-					failed++;
-					printf("psl_registrable_domain(%s)=%s (expected %s)\n", domain, result, expected_regdom);
-				} else ok++;
+			// there are test cases with 'example' unlisted TLD, unsure how to handle these, so skip for the moment
+			{
+				size_t len;
+
+				if ((len = strlen(domain)) >= 7 && !strcmp(domain + len - 7, "example"))
+					continue;
 			}
+
+			if (!strcmp(expected_regdom, "null"))
+				test(psl, domain, NULL);
+			else
+				test(psl, domain, expected_regdom);
 		}
 
 		fclose(fp);