Java Custom Exception

core-java/src/test/java/com/baeldung/customexception/IncorrectFileExtensionExceptionUnitTest.java

@@ -0,0 +1,29 @@
+package com.baeldung.customexception;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.io.File;
+
+import org.junit.Test;
+
+public class IncorrectFileExtensionExceptionUnitTest {
+
+    @Test
+    public void testWhenCorrectFileExtensionGiven_ReceivesNoException() throws IncorrectFileNameException {
+        assertThat(FileManager.getFirstLine("correctFileNameWithProperExtension.txt")).isEqualTo("Default First Line");
+    }
+
+    @Test(expected = IncorrectFileExtensionException.class)
+    public void testWhenCorrectFileNameExceptionThrown_ReceivesNoException() throws IncorrectFileNameException {
+        StringBuffer sBuffer = new StringBuffer();
+        sBuffer.append("src");
+        sBuffer.append(File.separator);
+        sBuffer.append("test");
+        sBuffer.append(File.separator);
+        sBuffer.append("resources");
+        sBuffer.append(File.separator);
+        sBuffer.append("correctFileNameWithoutProperExtension");
+        FileManager.getFirstLine(sBuffer.toString());
+    }
+
+}

core-java/src/test/java/com/baeldung/customexception/IncorrectFileNameExceptionUnitTest.java

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+package com.baeldung.customexception;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.Test;
+
+public class IncorrectFileNameExceptionUnitTest {
+
+    @Test(expected = IncorrectFileNameException.class)
+    public void testWhenIncorrectFileNameExceptionThrown_ReceivesIncorrectFileNameException() throws IncorrectFileNameException {
+        FileManager.getFirstLine("wrongFileName.txt");
+    }
+
+    @Test
+    public void testWhenCorrectFileNameExceptionThrown_ReceivesNoException() throws IncorrectFileNameException {
+        assertThat(FileManager.getFirstLine("correctFileName.txt")).isEqualTo("Default First Line");
+    }
+
+}