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Spock is a testing and specification framework for Java and Groovy applications. What makes it stand out from the crowd is its beautiful and highly expressive specification language. Thanks to its JUnit runner, Spock is compatible with most IDEs, build tools, and continuous integration servers. Spock is inspired from JUnit, jMock, RSpec, Groovy, Scala, Vulcans, and other fascinating life forms.

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/*
 * Copyright 2010 the original author or authors.
 *
 * Licensed 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
 *
 *     https://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 spock.util.matcher

import org.hamcrest.TypeSafeMatcher
import org.hamcrest.Description

/**
 * Generalization of org.hamcrest.number.IsCloseTo to arbitrary
 * Numbers (in particular BigDecimals). Otherwise almost
 * identical to that class.
 */
class IsCloseTo extends TypeSafeMatcher {
  private final Number value
  private final Number epsilon

  IsCloseTo(Number value, Number epsilon) {
    this.value = value
    this.epsilon = epsilon
  }

  @Override
  boolean matchesSafely(Number item) {
    delta(item) <= epsilon
  }

  @Override
  void describeMismatchSafely(Number item, Description mismatchDescription) {
    mismatchDescription.appendValue(item)
        .appendText(" differed by ")
        .appendValue(delta(item))
  }

  void describeTo(Description description) {
    description.appendText("a numeric value within ")
        .appendValue(epsilon)
        .appendText(" of ")
        .appendValue(value)
  }

  private Number delta(Number item) {
    // handle special values (infinity, nan)
    if (item == value) return 0

    (item - value).abs()
  }
}