08_assertRelativelyEquals.md

An example of test assertion with epsilon precision

// In org.apache.commons.math3.TestUtils

    /**
     * Verifies that the relative error in actual vs. expected is less than or
     * equal to relativeError.  If expected is infinite or NaN, actual must be
     * the same (NaN or infinity of the same sign).
     *
     * @param msg  message to return with failure
     * @param expected expected value
     * @param actual  observed value
     * @param relativeError  maximum allowable relative error
     */
    public static void assertRelativelyEquals(String msg, double expected,
            double actual, double relativeError) {
        if (Double.isNaN(expected)) {
            Assert.assertTrue(msg, Double.isNaN(actual));
        } else if (Double.isNaN(actual)) {
            Assert.assertTrue(msg, Double.isNaN(expected));
        } else if (Double.isInfinite(actual) || Double.isInfinite(expected)) {
            Assert.assertEquals(expected, actual, relativeError);
        } else if (expected == 0.0) {
            Assert.assertEquals(msg, actual, expected, relativeError);
        } else {
            double absError = FastMath.abs(expected) * relativeError;
            Assert.assertEquals(msg, expected, actual, absError);
        }
    }