Add unit test for FeaturesConfig class (knative-extensions#3771)

* Add unit test for FeaturesConfig class

* Update data-plane/core/src/test/java/dev/knative/eventing/kafka/broker/core/features/FeaturesConfigTest.java

Co-authored-by: Calum Murray <cmurray@redhat.com>

---------

Co-authored-by: Calum Murray <cmurray@redhat.com>

data-plane/core/src/test/java/dev/knative/eventing/kafka/broker/core/features/FeaturesConfigTest.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright © 2018 Knative Authors (knative-dev@googlegroups.com)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package dev.knative.eventing.kafka.broker.core.features;
+
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class FeaturesConfigTest {
+
+    private File featuresDir;
+
+    @BeforeEach
+    public void setup() throws IOException {
+        featuresDir = Files.createTempDirectory("features").toFile();
+
+        Files.createFile(Path.of(featuresDir.getAbsolutePath(), FeaturesConfig.KEY_AUTHENTICATION_OIDC))
+                .toFile();
+    }
+
+    @AfterEach
+    public void cleanup() throws IOException {
+        Files.walk(featuresDir.toPath())
+                .filter(Files::isRegularFile)
+                .map(Path::toFile)
+                .forEach(File::delete);
+
+        featuresDir.delete();
+    }
+
+    @Test
+    public void testFeaturesConfigAuthenticationOIDC() throws IOException {
+        FeaturesConfig fc = new FeaturesConfig(featuresDir.getAbsolutePath());
+        Assertions.assertFalse(fc.isAuthenticationOIDC(), "should be false, if feature file is empty");
+
+        try (FileWriter writer =
+                new FileWriter(Paths.get(featuresDir.getAbsolutePath(), FeaturesConfig.KEY_AUTHENTICATION_OIDC)
+                        .toString())) {
+            writer.write("enabled");
+        }
+
+        fc = new FeaturesConfig(featuresDir.getAbsolutePath());
+        Assertions.assertTrue(fc.isAuthenticationOIDC(), "should be true, if feature is enabled");
+    }
+}