Add test for expected exception

src/main/java/com/bmuschko/test/comparison/DefaultFileReader.java

@@ -8,6 +8,10 @@ public class DefaultFileReader implements FileReader {
 
     @Override
     public String readContent(Path path) throws IOException {
+        if (Files.notExists(path)) {
+            throw new IOException("File does not exist");
+        }
+
         return new String(Files.readAllBytes(path));
     }
 }

src/spockTest/groovy/com/bmuschko/test/comparison/spock/ExpectedExceptionTest.groovy

@@ -0,0 +1,19 @@
+package com.bmuschko.test.comparison.spock
+
+import com.bmuschko.test.comparison.DefaultFileReader
+import spock.lang.FailsWith
+import spock.lang.Specification
+import spock.lang.Subject
+
+import java.nio.file.Paths
+
+class ExpectedExceptionTest extends Specification {
+
+    @Subject def fileReader = new DefaultFileReader()
+
+    @FailsWith(IOException)
+    def "cannot read non-existent file"() {
+        expect:
+        fileReader.readContent(Paths.get('hello.text'))
+    }
+}

src/test/java/com/bmuschko/test/comparison/junit5/ExpectedExceptionTest.java

@@ -0,0 +1,21 @@
+package com.bmuschko.test.comparison.junit5;
+
+import com.bmuschko.test.comparison.DefaultFileReader;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.nio.file.Paths;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+public class ExpectedExceptionTest {
+
+    private final DefaultFileReader fileReader = new DefaultFileReader();
+
+    @Test
+    void cannotReadNonExistentFile() {
+        assertThrows(IOException.class, () -> {
+            fileReader.readContent(Paths.get("hello.text"));
+        });
+    }
+}