Add some tests for the LengthUtils class

Currently the LengthUtils class has no tests. This commit
adds some basic tests for the distance computations.

Author: tobias47n9e

app/src/test/java/fr/free/nrw/commons/LengthUtilsTest.java

@@ -0,0 +1,46 @@
+package fr.free.nrw.commons;
+
+import static org.hamcrest.CoreMatchers.is;
+
+import fr.free.nrw.commons.location.LatLng;
+import fr.free.nrw.commons.utils.LengthUtils;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class LengthUtilsTest {
+    @Test public void testZeroDistance() {
+        LatLng pointA = new LatLng(0, 0);
+        LatLng pointB = new LatLng(0, 0);
+        String distance = LengthUtils.formatDistanceBetween(pointA, pointB);
+        Assert.assertThat(distance, is("0m"));
+    }
+
+    @Test public void testOneDegreeOnEquator() {
+        LatLng pointA = new LatLng(0, 0);
+        LatLng pointB = new LatLng(0, 1);
+        String distance = LengthUtils.formatDistanceBetween(pointA, pointB);
+        Assert.assertThat(distance, is("111.2km"));
+    }
+
+    @Test public void testOneDegreeFortyFiveDegrees() {
+        LatLng pointA = new LatLng(45, 0);
+        LatLng pointB = new LatLng(45, 1);
+        String distance = LengthUtils.formatDistanceBetween(pointA, pointB);
+        Assert.assertThat(distance, is("78.6km"));
+    }
+
+    @Test public void testOneDegreeSouthPole() {
+        LatLng pointA = new LatLng(-90, 0);
+        LatLng pointB = new LatLng(-90, 1);
+        String distance = LengthUtils.formatDistanceBetween(pointA, pointB);
+        Assert.assertThat(distance, is("0m"));
+    }
+
+    @Test public void testPoleToPole() {
+        LatLng pointA = new LatLng(90, 0);
+        LatLng pointB = new LatLng(-90, 0);
+        String distance = LengthUtils.formatDistanceBetween(pointA, pointB);
+        Assert.assertThat(distance, is("20,015.1km"));
+    }
+}