halfhp#66 adds basic unit tests for CatmullRomInterpolator

halfhp · halfhp · commit dcddd7f6f5f0 · 2018-01-10T09:56:45.000-06:00
diff --git a/androidplot-core/src/main/java/com/androidplot/xy/CatmullRomInterpolator.java b/androidplot-core/src/main/java/com/androidplot/xy/CatmullRomInterpolator.java
@@ -20,7 +20,7 @@
 import java.util.List;
 
 /**
- * A primitive implementation of Catmull-Rom interpolation, based on the information found at:
+ * An implementation of Catmull-Rom interpolation, based on the information found at:
  * http://stackoverflow.com/questions/9489736/catmull-rom-curve-with-no-cusps-and-no-self-intersections/19283471#19283471
  */
 public class CatmullRomInterpolator implements Interpolator<CatmullRomInterpolator.Params> {
@@ -196,7 +196,7 @@ public List<XYCoords> interpolate(XYSeries series, Params params) {
      * @return the list of coordinates that define the CatmullRom curve
      * between the points defined by index+1 and index+2.
      */
-    public List<XYCoords> interpolate(XYSeries series, int index, Params params) {
+    protected List<XYCoords> interpolate(XYSeries series, int index, Params params) {
         List<XYCoords> result = new ArrayList<>();
         double[] x = new double[4];
         double[] y = new double[4];
@@ -251,7 +251,7 @@ public List<XYCoords> interpolate(XYSeries series, int index, Params params) {
      *             position between p1 and p2 to interpolate the value.
      * @return
      */
-    public static double interpolate(double[] p, double[] time, double t) {
+    protected static double interpolate(double[] p, double[] time, double t) {
         double L01 = p[0] * (time[1] - t) / (time[1] - time[0]) + p[1] * (t - time[0]) / (time[1] - time[0]);
         double L12 = p[1] * (time[2] - t) / (time[2] - time[1]) + p[2] * (t - time[1]) / (time[2] - time[1]);
         double L23 = p[2] * (time[3] - t) / (time[3] - time[2]) + p[3] * (t - time[2]) / (time[3] - time[2]);
diff --git a/androidplot-core/src/test/java/com/androidplot/xy/CatmullRomInterpolatorTest.java b/androidplot-core/src/test/java/com/androidplot/xy/CatmullRomInterpolatorTest.java
@@ -0,0 +1,59 @@
+package com.androidplot.xy;
+
+import org.junit.Test;
+
+import java.util.List;
+
+import static junit.framework.Assert.assertEquals;
+import static org.mockito.Mockito.mock;
+
+public class CatmullRomInterpolatorTest {
+
+    @Test(expected = IllegalArgumentException.class)
+    public void interpolate_invalidPointsPerSegment_throwsIllegalArgumentException() {
+        final XYSeries series = mock(XYSeries.class);
+        final CatmullRomInterpolator.Params params =
+                new CatmullRomInterpolator.Params(1, CatmullRomInterpolator.Type.Centripetal);
+
+        new CatmullRomInterpolator().interpolate(series, params);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void interpolate_twoElementSeries_throwsIllegalArgumentException() {
+        final XYSeries series = new SimpleXYSeries(SimpleXYSeries.ArrayFormat.Y_VALS_ONLY, "test", 1, 2);
+        final CatmullRomInterpolator.Params params =
+                new CatmullRomInterpolator.Params(2, CatmullRomInterpolator.Type.Centripetal);
+
+        new CatmullRomInterpolator().interpolate(series, params);
+    }
+
+    @Test
+    public void interpolate_threeElementSeriesAndThreePointsPerSegment_producesFivePoints() {
+        final XYSeries series = new SimpleXYSeries(SimpleXYSeries.ArrayFormat.Y_VALS_ONLY, "test", 1, 2, 3);
+        final CatmullRomInterpolator.Params params =
+                new CatmullRomInterpolator.Params(3, CatmullRomInterpolator.Type.Centripetal);
+        final List<XYCoords> interpolated = new CatmullRomInterpolator().interpolate(series, params);
+
+        assertEquals(5, interpolated.size());
+
+        // control points should exactly match input:
+        assertEquals(1, interpolated.get(0).y);
+        assertEquals(2, interpolated.get(2).y);
+        assertEquals(3, interpolated.get(4).y);
+    }
+
+    @Test
+    public void interpolate_threeElementSeriesAndFourPointsPerSegment_producesSavenPoints() {
+        final XYSeries series = new SimpleXYSeries(SimpleXYSeries.ArrayFormat.Y_VALS_ONLY, "test", 1, 2, 3);
+        final CatmullRomInterpolator.Params params =
+                new CatmullRomInterpolator.Params(4, CatmullRomInterpolator.Type.Centripetal);
+        final List<XYCoords> interpolated = new CatmullRomInterpolator().interpolate(series, params);
+
+        assertEquals(7, interpolated.size());
+
+        // control points should exactly match input:
+        assertEquals(1, interpolated.get(0).y);
+        assertEquals(2, interpolated.get(3).y);
+        assertEquals(3, interpolated.get(6).y);
+    }
+}
