commons-numbers-arrays/src/test/java/org/apache/commons/numbers/arrays/CosAngleTest.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with this
 * work for additional information regarding copyright ownership. The ASF
 * licenses this file to You under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law
 * or agreed to in writing, software distributed under the License is
 * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */
package org.apache.commons.numbers.arrays;

import org.junit.Assert;
import org.junit.jupiter.api.Test;

/**
 * Test cases for the {@link CosAngle} class.
 */
public class CosAngleTest {
    @Test
    public void testCosAngle2D() {
        double expected;

        final double[] v1 = { 1, 0 };
        expected = 1;
        Assert.assertEquals(expected, CosAngle.value(v1, v1), 0d);

        final double[] v2 = { 0, 1 };
        expected = 0;
        Assert.assertEquals(expected, CosAngle.value(v1, v2), 0d);

        final double[] v3 = { 7, 7 };
        expected = Math.sqrt(2) / 2;
        Assert.assertEquals(expected, CosAngle.value(v1, v3), 1e-15);
        Assert.assertEquals(expected, CosAngle.value(v3, v2), 1e-15);

        final double[] v4 = { -5, 0 };
        expected = -1;
        Assert.assertEquals(expected, CosAngle.value(v1, v4), 0);

        final double[] v5 = { -100, 100 };
        expected = 0;
        Assert.assertEquals(expected, CosAngle.value(v3, v5), 0);
    }

    @Test
    public void testCosAngle3D() {
        double expected;

        final double[] v1 = { 1, 1, 0 };
        expected = 1;
        Assert.assertEquals(expected, CosAngle.value(v1, v1), 1e-15);

        final double[] v2 = { 1, 1, 1 };
        expected = Math.sqrt(2) / Math.sqrt(3);
        Assert.assertEquals(expected, CosAngle.value(v1, v2), 1e-15);
    }

    @Test
    public void testCosAngleExtreme() {
        double expected;

        final double tiny = 1e-200;
        final double[] v1 = { tiny, tiny };
        final double big = 1e200;
        final double[] v2 = { -big, -big };
        expected = -1;
        Assert.assertEquals(expected, CosAngle.value(v1, v2), 1e-15);

        final double[] v3 = { big, -big };
        expected = 0;
        Assert.assertEquals(expected, CosAngle.value(v1, v3), 1e-15);
    }
}