Polishing

junit-engine-api/src/main/java/org/junit/gen5/engine/ConfigurationParameters.java

@@ -21,7 +21,9 @@
  */
 @API(Experimental)
 public interface ConfigurationParameters {
+
 	Optional<String> get(String key);
 
 	int getSize();
+
 }

junit-launcher/src/main/java/org/junit/gen5/launcher/PostDiscoveryFilter.java

@@ -19,7 +19,8 @@
 
 /**
  * A {@code PostDiscoveryFilter} filters particular tests after test discovery.
- * These filters must not be applied by the {@link TestEngine} during test
+ *
+ * <p>These filters must not be applied by a {@link TestEngine} during test
  * discovery.
  *
  * @since 5.0

junit-launcher/src/main/java/org/junit/gen5/launcher/TestDiscoveryRequest.java

@@ -22,12 +22,11 @@
 import org.junit.gen5.engine.EngineDiscoveryRequest;
 
 /**
- * This class extends the {@link EngineDiscoveryRequest}
- * by providing access to filters which are applied by the
- * {@link Launcher} itself
+ * {@code TestDiscoveryRequest} is an extension of {@link EngineDiscoveryRequest}
+ * that provides access to filters which are applied by the {@link Launcher} itself.
  *
- * <p>Moreover, the add*-methods can be used by external clients
- * that do not want to use the
+ * <p>Moreover, the {@code add*()} methods can be used by external clients that
+ * do not want to use the
  * {@link org.junit.gen5.launcher.main.TestDiscoveryRequestBuilder}.
  *
  * @since 5.0
@@ -51,7 +50,7 @@ public interface TestDiscoveryRequest extends EngineDiscoveryRequest {
 
 	void addPostFilters(Collection<PostDiscoveryFilter> postDiscoveryFilters);
 
-	void addConfigurationParameters(Map<String, String> launchParameters);
+	void addConfigurationParameters(Map<String, String> configurationParameters);
 
 	List<EngineIdFilter> getEngineIdFilters();
 

junit-launcher/src/main/java/org/junit/gen5/launcher/main/DiscoveryRequest.java

@@ -27,21 +27,21 @@
 import org.junit.gen5.launcher.TestDiscoveryRequest;
 
 /**
- * The {@code DiscoveryRequest} represents the configuration for the test
+ * {@code DiscoveryRequest} represents the configuration for test
  * discovery and execution. It is passed to every active {@link TestEngine}
- * and should be used to lookup tests for the given configuration.
+ * and should be used to look up tests for the given configuration.
  *
  * <p>A {@code DiscoveryRequest} contains different configuration options.
  *
  * <ul>
- * <li>{@link DiscoverySelector}: A selector defines location(s) a
- * {@link TestEngine} should lookup tests at</li>
- * <li>{@link EngineIdFilter}: A special filter that is applied before an
- * {@link TestEngine} is executed</li>
- * <li>{@link DiscoveryFilter}: A filter that should be applied by the
- * {@link TestEngine} during test discovery.</li>
- * <li>{@link PostDiscoveryFilter}: A filter that will be applied after
- * test discovery.</li>
+ * <li>{@link DiscoverySelector}: A selector defines where a {@code TestEngine}
+ * should look up tests</li>
+ * <li>{@link EngineIdFilter}: A special filter that is applied before each
+ * {@code TestEngine} is executed</li>
+ * <li>{@link DiscoveryFilter}: A filter that should be applied by
+ * {@code TestEngines} during test discovery</li>
+ * <li>{@link PostDiscoveryFilter}: A filter that will be applied by the
+ * launcher after {@code TestEngines} have performed test discovery</li>
  * </ul>
  *
  * @since 5.0
@@ -58,13 +58,13 @@ final class DiscoveryRequest implements TestDiscoveryRequest {
 	// Filter based on the engine id
 	private final List<EngineIdFilter> engineIdFilters = new LinkedList<>();
 
-	// Discovery filters are handed through to all test engines to be applied during discovery
+	// Discovery filters are handed through to all engines to be applied during discovery.
 	private final List<DiscoveryFilter<?>> discoveryFilters = new LinkedList<>();
 
-	// Descriptor Filters are evaluated by the launcher itself after engines have done their discovery.
+	// Descriptor filters are applied by the launcher itself after engines have performed discovery.
 	private final List<PostDiscoveryFilter> postDiscoveryFilters = new LinkedList<>();
 
-	// Additional Configuration Parameters can be used to provide configuration, e.g. for extensions
+	// Configuration parameters can be used to provide custom configuration to engines, e.g. for extensions
 	private final LauncherConfigurationParameters configurationParameters = new LauncherConfigurationParameters();
 
 	@Override
@@ -141,4 +141,5 @@ public void addConfigurationParameters(Map<String, String> configurationParamete
 	public ConfigurationParameters getConfigurationParameters() {
 		return this.configurationParameters;
 	}
+
 }

junit-launcher/src/main/java/org/junit/gen5/launcher/main/LauncherConfigurationParameters.java

@@ -24,6 +24,7 @@
  */
 @API(Experimental)
 class LauncherConfigurationParameters implements ConfigurationParameters {
+
 	private final Map<String, String> configurationParameters = new HashMap<>();
 
 	@Override
@@ -33,10 +34,11 @@ public Optional<String> get(String key) {
 
 	@Override
 	public int getSize() {
-		return configurationParameters.size();
+		return this.configurationParameters.size();
 	}
 
 	void addAll(Map<String, String> configurationParameters) {
 		this.configurationParameters.putAll(configurationParameters);
 	}
+
 }

junit-launcher/src/main/java/org/junit/gen5/launcher/main/TestDiscoveryRequestBuilder.java

@@ -20,6 +20,7 @@
 
 import org.junit.gen5.commons.meta.API;
 import org.junit.gen5.commons.util.PreconditionViolationException;
+import org.junit.gen5.commons.util.Preconditions;
 import org.junit.gen5.engine.DiscoveryFilter;
 import org.junit.gen5.engine.DiscoverySelector;
 import org.junit.gen5.engine.Filter;
@@ -28,13 +29,13 @@
 import org.junit.gen5.launcher.TestDiscoveryRequest;
 
 /**
- * The {@code DiscoveryRequestBuilder} provides a light-weight DSL for
+ * The {@code TestDiscoveryRequestBuilder} provides a light-weight DSL for
  * generating a {@link TestDiscoveryRequest}.
  *
  * <h4>Example</h4>
  *
  * <pre style="code">
- *   DiscoveryRequestBuilder.request()
+ *   TestDiscoveryRequestBuilder.request()
  *     .select(
  *       forPackageName("org.junit.gen5"),
  *       forPackageName("com.junit.samples"),
@@ -95,12 +96,15 @@ public TestDiscoveryRequestBuilder filter(Filter<?>... filters) {
 	}
 
 	public TestDiscoveryRequestBuilder configurationParameter(String key, String value) {
-		configurationParameters.put(key, value);
+		Preconditions.notBlank(key, "key must not be null or empty");
+		this.configurationParameters.put(key, value);
 		return this;
 	}
 
 	public TestDiscoveryRequestBuilder configurationParameters(Map<String, String> configurationParameters) {
-		configurationParameters.forEach(this::configurationParameter);
+		if (configurationParameters != null) {
+			configurationParameters.forEach(this::configurationParameter);
+		}
 		return this;
 	}