Created JUnit tests for Day007.class

days/day007/pom.xml

@@ -11,5 +11,17 @@
 
     <artifactId>day007</artifactId>
 
+    <dependencies>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
 
 </project>

days/day007/src/test/java/com/thegreatapi/ahundreddaysofjava/day007/Day007Test.java

@@ -0,0 +1,46 @@
+package com.thegreatapi.ahundreddaysofjava.day007;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.text.MessageFormat;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.junit.jupiter.api.AfterEach;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class Day007Test {
+
+    private final PrintStream standardOut = System.out;
+    private final ByteArrayOutputStream outputStreamCaptor = new ByteArrayOutputStream();
+
+    @BeforeEach
+    public void setUp() {
+        System.setOut(new PrintStream(outputStreamCaptor));
+    }
+
+    @Test
+    void shouldFormatMessageCorrectly() {
+        // Arrange
+        String param1 = "Hello";
+        String param2 = "World";
+        String param3 = "Java";
+
+        // Act
+        String actualMessage = MessageFormat.format(
+                "This message contains 3 parameters. The #1 is ''{0}'', "
+                + "the #2 is ''{1}'', and the #3 is ''{2}''.",
+                param1, param2, param3);
+
+        // Assert
+        String expectedMessage = "This message contains 3 parameters. The #1 is"
+                + " 'Hello', the #2 is 'World', and the #3 is 'Java'.";
+        assertThat(actualMessage).isEqualTo(expectedMessage);
+        //assertEquals(expectedMessage, outputStreamCaptor.toString().trim());
+    }
+
+    @AfterEach
+    public void tearDown() {
+        System.setOut(standardOut);
+    }
+}