diff --git a/tests/Makefile b/tests/Makefile
new file mode 100644
index 0000000..eccfa59
--- /dev/null
+++ b/tests/Makefile
@@ -0,0 +1,4 @@
+.PHONY: test
+test:
+	cat ../THREAD_TABLE.scad | awk -f test_table.awk
+
diff --git a/tests/test_table.awk b/tests/test_table.awk
index 5fa289f..0af95a1 100644
--- a/tests/test_table.awk
+++ b/tests/test_table.awk
@@ -25,8 +25,10 @@ function slope(x, y) {
 
 function test_horizontal() {
 	# test whether v0 and v1 as well as v2 and v3 have the same radius
-	if (v0[1] != v1[1] || v2[1] != v3[1])
+	if (v0[1] != v1[1] || v2[1] != v3[1]) {
 		print designator " FAIL: not horizontal";
+		PASS = 0;
+	}
 }
 
 BEGIN	{
@@ -35,20 +37,52 @@ BEGIN	{
 	pi = atan2(0, -1);
 	deg = pi / 180;
 	dphi = 0.001;
+
+	PASS = 1;
 	}
 
 { 	# first match-all rule: set state to untested
 	tested = 0;
 }
 
+/"[^,]+-ext/ {
+	# external threads have positive Rrot 
+	parse();
+	if (Rrot < 0) {
+		print designator " FAIL: negative radius of rotation";
+		PASS = 0;
+	}
+	# test overlapp between thread and support
+	if (Rrot > Dsupport / 2) {
+		print designator " FAIL: Rsupport < Rrot";
+		PASS = 0;
+	}
+}
+
+/"[^,]+-int/ {
+	# internal threads have negative Rrot 
+	parse();
+	if (Rrot > 0) {
+		print designator " FAIL: positive radius of rotation";
+		PASS = 0;
+	}
+	# test overlapp between thread and support
+	if (-Rrot < Dsupport / 2) {
+		print designator " FAIL: Rsupport > Rrot";
+		PASS = 0;
+	}
+}
+
 /M[0-9.x-]+-ext/ {
 	# ext M threads have +/-60 deg slopes, horizontal crest / valley
 	parse();
 	m1 = slope(v0, v3) / deg;
 	m2 = slope(v2, v1) / deg;
 	if (m1 > 60 + dphi || m1 < 60 - dphi \
-	    || m2 < -60 - dphi || m2 > -60 + dphi)
+	    || m2 < -60 - dphi || m2 > -60 + dphi) {
 		print designator " FAIL: " m1 ", " m2 " deg";
+		PASS = 0;
+	};
 	test_horizontal();
 	tested = 1;
 }
@@ -59,8 +93,10 @@ BEGIN	{
 	m1 = slope(v3, v0) / deg;
 	m2 = slope(v1, v2) / deg;
 	if (m1 > -60 + dphi || m1 < -60 - dphi \
-	    || m2 < 60 - dphi || m2 > 60 + dphi)
+	    || m2 < 60 - dphi || m2 > 60 + dphi) {
 		print designator " FAIL: " m1 ", " m2 " deg";
+		PASS = 0;
+	}
 	test_horizontal();
 	tested = 1;
 }
@@ -71,8 +107,10 @@ BEGIN	{
 	m1 = slope(v0, v3) / deg;
 	m2 = slope(v2, v1) / deg;
 	if (m1 > 62.5 + dphi || m1 < 62.5 - dphi \
-	    || m2 < -62.5 - dphi || m2 > -62.5 + dphi)
+	    || m2 < -62.5 - dphi || m2 > -62.5 + dphi) {
 		print designator " FAIL: " m1 ", " m2 " deg";
+		PASS = 0;
+	}
 	test_horizontal();
 	tested = 1;
 }
@@ -83,8 +121,10 @@ BEGIN	{
 	m1 = slope(v3, v0) / deg;
 	m2 = slope(v1, v2) / deg;
 	if (m1 > -62.5 + dphi || m1 < -62.5 - dphi \
-	    || m2 < 62.5 - dphi || m2 > 62.5 + dphi)
+	    || m2 < 62.5 - dphi || m2 > 62.5 + dphi) {
 		print designator " FAIL: " m1 ", " m2 " deg";
+		PASS = 0;
+	}
 	test_horizontal();
 	tested = 1;
 }
@@ -96,8 +136,10 @@ BEGIN	{
 	m1 = slope(v0, v3) / deg;
 	m2 = slope(v2, v1) / deg;
 	if (m1 > 70 + dphi || m1 < 70 - dphi \
-	    || m2 < -80 - dphi || m2 > -80 + dphi)
+	    || m2 < -80 - dphi || m2 > -80 + dphi) {
 		print designator " FAIL: " m1 ", " m2 " deg";
+		PASS = 0;
+	}
 	test_horizontal();
 	tested = 1;
 }
@@ -109,8 +151,10 @@ BEGIN	{
 	m1 = slope(v3, v0) / deg;
 	m2 = slope(v1, v2) / deg;
 	if (m1 > -70 + dphi || m1 < -70 - dphi \
-	    || m2 < 80 - dphi || m2 > 80 + dphi)
+	    || m2 < 80 - dphi || m2 > 80 + dphi) {
 		print designator " FAIL: " m1 ", " m2 " deg";
+		PASS = 0;
+	}
 	test_horizontal();
 	tested = 1;
 }
@@ -121,6 +165,12 @@ BEGIN	{
 	if (tested == 0) {
 		parse();
 		print designator " FAIL: not tested";
+		PASS = 0;
 	};
 }
 
+END {
+	if (PASS == 1) print "TESTS SUCCESSFUL"
+	else print "TESTS FAIL";
+}
+