feat(test): add testing with files in Main

app/src/test/java/MainTest.java

@@ -6,6 +6,8 @@ import java.io.IOException;
 import java.io.PrintStream;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
 
 import static org.junit.jupiter.api.Assertions.*;
 
@@ -73,9 +75,64 @@ class MainTest {
 		// Check that the program quit at the expected point, with expected output
 		assertEquals("Invalid arguments, you need to define the text file to read from!\n", outContent.toString());
 	}
+	
+	@Test
+	@DisplayName("Invalid/Nonexistent file")
+	void invalidFile() {
+		arguments = new String[1];
+		
+		arguments[0] = "doesNotExist.txt";
+		
+		assertThrowsExactly(RuntimeException.class, () -> Main.main(arguments));
+	}
 
 	@Test
 	@DisplayName("Normal test run")
-	void normalRun() {
+	void normalRun() throws IOException {
+		// List of emails to add to the file
+		List<String> emails = new ArrayList<>() {{
+			add("johndoe@gmail.com");
+			add("janedoe@gmail.com");
+			add("person@outlook.com");
+			add("totallylegitpresident@gmail.com");
+			add("google@yahoo.com");
+			add("person1st@outlook.com");
+			add("google+scam@gmail.com");
+		}};
+		
+		Files.write(tempFile, emails);
+		
+		// The expected output - \n has been added on the end due to the program quitting at the end
+		String expectedOutput = "gmail.com 4\noutlook.com 2\nyahoo.com 1\n";
+		
+		// Add argument for filepath
+		arguments[0] = tempFile.toString();
+		
+		Main.main(arguments);
+		
+		assertEquals(expectedOutput, outContent.toString());
+	}
+	
+	@Test
+	@DisplayName("File with invalid emails")
+	void brokenData() throws IOException {
+		// List of emails, with some of the emails being invalid
+		List<String> emails = new ArrayList<>() {{
+			add("gmail.com");
+			add("janedoe@gmail.com");
+			add("person@outlook.com");
+			add("totallylegit@president@gmail.com");
+			add("google@yahoo");
+			add("person1st@outlook,com");
+			add("google+scam@gmail.com");
+		}};
+
+		Files.write(tempFile, emails);
+
+		// Add argument for filepath
+		arguments[0] = tempFile.toString();
+		
+		// Checks for the fail from the email validation
+		assertThrowsExactly(IllegalArgumentException.class, () -> Main.main(arguments));
 	}
 }