DoubleDiffer.java

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package plotter;

import junit.framework.Assert;
import junit.framework.AssertionFailedError;

/**
 * Helper class for asserting that doubles are nearly equal.
 * @author Adam Crume
 */
public class DoubleDiffer {
	/** Allowable difference between doubles. */
	double error;


	/**
	 * Creates a {@link DoubleDiffer} with the given tolerance
	 * @param error maximum allowable difference between doubles
	 */
	public DoubleDiffer(double error) {
		this.error = error;
	}


	/**
	 * Asserts that the absolute value of the difference between the doubles is less than the tolerance.
	 * @param expected expected value
	 * @param actual actual value
	 * @throws AssertionFailedError if the doubles are farther apart than the tolerance allows
	 */
	public void assertClose(double expected, double actual) {
		Assert.assertTrue("Expected: " + expected + ", actual: " + actual, Math.abs(expected - actual) < error);
	}
}