Add test to ensure colours have white foreground

app/src/test/java/protect/card_locker/UtilsTest.java

@@ -0,0 +1,34 @@
+package protect.card_locker;
+
+import static org.junit.Assert.assertFalse;
+
+import android.content.res.TypedArray;
+import android.graphics.Color;
+
+import androidx.test.core.app.ActivityScenario;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+
+
+@RunWith(RobolectricTestRunner.class)
+public class UtilsTest {
+    /**
+     * Ensure all the default card colours (used when an user has not chosen a card colour) use white foreground text
+     */
+    @Test
+    public void allDefaultCardColoursHaveWhiteForegroundTest() {
+        try(ActivityScenario<MainActivity> scenario = ActivityScenario.launch(MainActivity.class)) {
+            scenario.onActivity(activity -> {
+                TypedArray colors = activity.getApplicationContext().getResources().obtainTypedArray(R.array.letter_tile_colors);
+
+                for (int i = 0; i < colors.length(); i++) {
+                    // Grab white as fallback so that if the retrieval somehow fails the test is guaranteed to fail because a white background will have black foreground
+                    int color = colors.getColor(i, Color.WHITE);
+                    assertFalse(Utils.needsDarkForeground(color));
+                }
+            });
+        }
+    }
+}