test: 후위 연산식을 계산하는 클래스 테스트 작성 및 통과

Author: wonu606

calculator/src/test/java/com/wonu606/calculator/PostCalculatorTest.java

@@ -0,0 +1,88 @@
+package com.wonu606.calculator;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.wonu606.calculator.calculator.Calculator;
+import com.wonu606.calculator.calculator.PostfixCalculator;
+import java.util.Arrays;
+import java.util.List;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+class PostCalculatorTest {
+
+    @Test
+    @DisplayName("연산자가 1개일 경우")
+    void testSingle() {
+        // given
+        Calculator calculator = new PostfixCalculator();
+        List<String> actualList = Arrays.asList("-3", "5.0", "+");
+        double expected = -3 + 5.0;
+
+        // when
+        double result = calculator.calculate(actualList);
+
+        // then
+        assertThat(result).isEqualTo(expected);
+    }
+
+    @Test
+    @DisplayName("같은 우선 순위일 경우")
+    void testPrecedenceEquals() {
+        // given
+        Calculator calculator = new PostfixCalculator();
+        List<String> actualList = Arrays.asList("3", "5", "+", "2", "-");
+        double expected = 3 + 5 - 2;
+
+        // when
+        double result = calculator.calculate(actualList);
+
+        // then
+        assertThat(result).isEqualTo(expected);
+    }
+
+    @Test
+    @DisplayName("높은 우선 순위가 뒤에 올 경우")
+    void testHigherPrecedenceFollows() {
+        // given
+        Calculator calculator = new PostfixCalculator();
+        List<String> actualList = Arrays.asList("3", "5", "2", "*", "+");
+        double expected = 3 + 5 * 2;
+
+        // when
+        double result = calculator.calculate(actualList);
+
+        // then
+        assertThat(result).isEqualTo(expected);
+    }
+
+    @Test
+    @DisplayName("높은 우선 순위가 앞에 올 경우")
+    void testHigherPrecedenceComesFirst() {
+        // given
+        Calculator calculator = new PostfixCalculator();
+        List<String> actualList = Arrays.asList("3", "5", "*", "2", "+");
+        double expected = 3 * 5 + 2;
+
+        // when
+        double result = calculator.calculate(actualList);
+
+        // then
+        assertThat(result).isEqualTo(expected);
+    }
+
+    @Test
+    @DisplayName("소수가 나올 경우")
+    void testIfFraction() {
+        // given
+        Calculator calculator = new PostfixCalculator();
+        List<String> actualList = Arrays.asList("3", "5", "/", "2", "+");
+        double expected = 3.0 / 5 + 2;
+
+        // when
+        double result = calculator.calculate(actualList);
+
+        // then
+        assertThat(result).isEqualTo(expected);
+    }
+}