test: 중위 연산식을 후위 연산식으로 변환하는 Converter 테스트 작성 및 통과

Author: wonu606

calculator/src/test/java/com/wonu606/calculator/converter/InfixToPostfixConverterTest.java

@@ -0,0 +1,71 @@
+package com.wonu606.calculator.converter;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Arrays;
+import java.util.List;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+class InfixToPostfixConverterTest {
+
+    @Test
+    @DisplayName("연산자가 1개일 경우")
+    void testSingle() {
+        // given
+        Converter<String, List<String>> converter = new InfixToPostfixConverter();
+        List<String> expectedList = Arrays.asList("-3", "5.0", "+");
+        String infixExpression = "-3 + 5.0";
+
+        // when
+        List<String> actualList = converter.convert(infixExpression);
+
+        // then
+        assertThat(actualList).isEqualTo(expectedList);
+    }
+
+    @Test
+    @DisplayName("같은 우선 순위일 경우")
+    void testPrecedenceEquals() {
+        // given
+        Converter<String, List<String>> converter = new InfixToPostfixConverter();
+        List<String> expectedList = Arrays.asList("3", "5", "+", "2", "-");
+        String infixExpression = "3 + 5 - 2";
+
+        // when
+        List<String> actualList = converter.convert(infixExpression);
+
+        // then
+        assertThat(actualList).isEqualTo(expectedList);
+    }
+
+    @Test
+    @DisplayName("높은 우선 순위가 뒤에 올 경우")
+    void testHigherPrecedenceFollows() {
+        // given
+        Converter<String, List<String>> converter = new InfixToPostfixConverter();
+        List<String> expectedList = Arrays.asList("3", "5", "2", "*", "+");
+        String infixExpression = "3 + 5 * 2";
+
+        // when
+        List<String> actualList = converter.convert(infixExpression);
+
+        // then
+        assertThat(actualList).isEqualTo(expectedList);
+    }
+
+    @Test
+    @DisplayName("높은 우선 순위가 앞에 올 경우")
+    void testHigherPrecedenceComesFirst() {
+        // given
+        Converter<String, List<String>> converter = new InfixToPostfixConverter();
+        List<String> expectedList = Arrays.asList("3", "5", "*", "2", "+");
+        String infixExpression = "3 * 5 + 2";
+
+        // when
+        List<String> actualList = converter.convert(infixExpression);
+
+        // then
+        assertThat(actualList).isEqualTo(expectedList);
+    }
+}

calculator/src/test/java/com/wonu606/validator/InfixValidatorTest.java

@@ -14,7 +14,7 @@ void testNotInfix() {
         Validator validator = new InfixValidator();
 
         // when
-        String expression = "+ 1 3";
+        String expression = "1 3 +";
 
         // then
         assertThat(validator.isValid(expression)).isFalse();