PatternTest.java

package com.hanserwei.patterns.strategy;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertThrows;

import org.junit.jupiter.api.Test;

/** 验证本模式的协作契约与边界行为. */
public final class PatternTest {
  /** 同一业务上下文可以装配不同算法. */
  @Test
  void switchesAlgorithms() {
    assertEquals(1000, new QuoteService(new FlatFee()).quote(600));
    assertEquals(1200, new QuoteService(new PerWordFee(2)).quote(600));
    assertEquals(0, new QuoteService(new PerWordFee(2)).quote(0));
  }

  /** 所有策略遵守非负输入约定，并显式报告溢出. */
  @Test
  void validatesAlgorithmBoundaries() {
    assertThrows(IllegalArgumentException.class, () -> new FlatFee().fee(-1));
    assertThrows(IllegalArgumentException.class, () -> new PerWordFee(2).fee(-1));
    assertThrows(IllegalArgumentException.class, () -> new PerWordFee(-1));
    assertThrows(ArithmeticException.class, () -> new PerWordFee(Long.MAX_VALUE).fee(2));
  }
}