feat: add reading file test

app/src/test/java/ReadFileTest.java

@@ -51,5 +51,26 @@ class ReadFileTest {
 			
 			assertThrowsExactly(RuntimeException.class, () -> ReadFile.open(nonExistent));
 		}
+		
+		@Test
+		@DisplayName("Reading valid file correctly")
+		void openValidFile() throws IOException {
+			String filename = "test.txt";
+			Path path = Files.createFile(tempDir.resolve(filename));
+
+			List<String> emails = new ArrayList<>() {{
+				add("test@test.com");
+				add("person@gmail.com");
+				add("hello@outlook.com");
+			}};
+
+			// Write the emails to the file "test.txt"
+			Files.write(path, emails);
+
+			// Get the output from the function
+			List<String> output = ReadFile.open(path);
+
+			assertEquals(emails, output);
+		}
 	}
 }