AmountCloseTo.java: added factory method with custom error

    showing unit of first item in description

src/test/java/org/hamcrest/AmountCloseTo.java

@@ -2,34 +2,55 @@ package org.hamcrest;
 
 import static org.hamcrest.Matchers.closeTo;
 
-import org.hamcrest.Description;
-import org.hamcrest.Factory;
-import org.hamcrest.Matchers;
-import org.hamcrest.TypeSafeMatcher;
+import javax.measure.unit.Unit;
+
+import org.hamcrest.number.IsCloseTo;
 import org.jscience.physics.amount.Amount;
 
+/**
+ * {@code IsCloseTo} implementation for {@link Amount}.
+ * 
+ * @see IsCloseTo
+ * @author mey
+ *
+ */
 public class AmountCloseTo extends TypeSafeMatcher<Amount<?>> {
+    private static final double DEFAULT_ERROR = 1E-14d;
+
     private final Amount<?> amount;
-    private static final double MAX_ERROR = 1E-14d;
+    private final double error;
 
-    AmountCloseTo(Class<?> expectedType, Amount<?> amount) {
+    public AmountCloseTo(Class<?> expectedType, Amount<?> amount, double error) {
 	super(expectedType);
 	this.amount = amount;
+	this.error = error;
     }
 
     @Override
     public void describeTo(Description description) {
-	closeTo(amount.getEstimatedValue(), MAX_ERROR).describeTo(description);
+	closeTo(amount.getEstimatedValue(), error).describeTo(description);
+	description.appendText(" ").appendValue(amount.getUnit());
     }
 
     @Override
     protected boolean matchesSafely(Amount<?> item) {
-	return Matchers.closeTo(amount.getEstimatedValue(), MAX_ERROR)
-		.matches(item.to(amount.getUnit()).getEstimatedValue());
+	Unit<?> unit = amount.getUnit();
+	return Matchers.closeTo(amount.getEstimatedValue(), error)
+		.matches(item.to(unit).getEstimatedValue());
+    }
+
+    /**
+     * 
+     * @param amount
+     * @return {@link Matcher} with default error
+     */
+    @Factory
+    public static Matcher<Amount<?>> amountCloseTo(final Amount<?> amount) {
+	return amountCloseTo(amount, DEFAULT_ERROR);
     }
 
     @Factory
-    public static org.hamcrest.Matcher<Amount<?>> amountCloseTo(final Amount<?> amount) {
-	return new AmountCloseTo(Amount.class, amount);
+    public static Matcher<Amount<?>> amountCloseTo(final Amount<?> amount, double error) {
+	return new AmountCloseTo(Amount.class, amount, error);
     }
 }
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