tried to add test

src/unittest.scad

@@ -0,0 +1,54 @@
+module fail(message) {
+    echo(
+        str( 
+            "<b>",
+                "<span style='color: red'>", 
+                    "FAIL", 
+                "</span>", 
+            "</b>"
+        )
+    );
+    if(message != undef) {
+        echo(
+            str( 
+                "<b>",
+                    "<span style='color: red'>　",
+                        message, 
+                    "</span>", 
+                "</b>"
+            )
+        );
+    }
+}
+
+module assertEqualPoint(expected, actual) {
+    n = 10000;
+
+    function shift_to_int(pt, n) = 
+        len(pt) == 2 ? 
+            [round(pt[0] * n), round(pt[1] * n)] :
+            [round(pt[0] * n), round(pt[1] * n), round(pt[2] * n)];
+    
+    shifted_expected = shift_to_int(
+        expected, 
+        n
+    );    
+
+    shifted_actual = shift_to_int(
+        actual, 
+        n
+    );
+    
+    if(shifted_expected != shifted_actual) {
+        fail(
+            str("expected: ", expected,
+            ", but: ", actual)
+        );
+    }
+}
+
+module assertEqualPoints(expected, actual) {
+    for(i = [0:len(actual) - 1]) {        
+        assertEqualPoint(expected[i], actual[i]);
+    }
+}

test/test_shape_arc.scad

@@ -0,0 +1,11 @@
+include <unittest.scad>;
+include <shape_arc.scad>;
+
+echo("==== test_sharp_arc ====");
+
+expected_shape_pts = [[0, -12.4315], [1.30661, -12.4315], [3.86271, -11.8882], [6.25, -10.8253], [8.36413, -9.28931], [10.1127, -7.34732], [11.4193, -5.08421], [12.2268, -2.5989], [12.5, 0], [12.2268, 2.5989], [11.4193, 5.08421], [10.1127, 7.34732], [8.36413, 9.28931], [6.25, 10.8253], [3.86271, 11.8882], [1.30661, 12.4315], [0, 12.4315], [0, 7.45891], [0.783963, 7.45891], [2.31763, 7.13292], [3.75, 6.49519], [5.01848, 5.57359], [6.06763, 4.40839], [6.85159, 3.05052], [7.33611, 1.55934], [7.5, 0], [7.33611, -1.55934], [6.85159, -3.05052], [6.06763, -4.40839], [5.01848, -5.57359], [3.75, -6.49519], [2.31763, -7.13292], [0.783963, -7.45891], [0, -7.45891]];
+
+shape_pts = shape_arc(radius = 10, angle = [-90, 90], width = 5);
+
+assertEqualPoints(expected_shape_pts, shape_pts);
+