region: add a single 'covers' test

test/region.cpp

@@ -111,6 +111,29 @@ main (int, char **)
         );
     };
 
+    // Check that 'covers' behaves as expected. ie, a covers b.
+    {
+        using p = cruft::point2i;
+        using e = cruft::extent2i;
+
+        struct {
+            cruft::region2i a;
+            cruft::region2i b;
+            bool expected;
+            char const *message;
+        } TESTS[] = {
+            {
+                .a = { p {  0,  0, }, e { 32, 32, } },
+                .b = { p { 27,  4, }, e {  8, 13, } },
+                .expected = false,
+                .message = "a exceeds +x margin",
+            }
+        };
+
+        for (auto const &[a, b, expected, msg]: TESTS)
+            tap.expect_eq (a.covers (b), expected, "covers: %!", msg);
+    }
+
     // ensure make_region covers the expected values
     {
         const cruft::region2i REGION {