Make injection type explicit.

Makes it easier to understand the code.

Author: stefanbirkner

src/main/java/org/junit/runners/parameterized/BlockJUnit4ClassRunnerWithParameters.java

@@ -18,6 +18,10 @@
  */
 public class BlockJUnit4ClassRunnerWithParameters extends
         BlockJUnit4ClassRunner {
+    private enum InjectionType {
+        CONSTRUCTOR, FIELD
+    }
+
     private final Object[] parameters;
 
     private final String name;
@@ -32,10 +36,15 @@ public BlockJUnit4ClassRunnerWithParameters(TestWithParameters test)
 
     @Override
     public Object createTest() throws Exception {
-        if (fieldsAreAnnotated()) {
-            return createTestUsingFieldInjection();
-        } else {
-            return createTestUsingConstructorInjection();
+        InjectionType injectionType = getInjectionType();
+        switch (injectionType) {
+            case CONSTRUCTOR:
+                return createTestUsingConstructorInjection();
+            case FIELD:
+                return createTestUsingFieldInjection();
+            default:
+                throw new IllegalStateException("The injection type "
+                        + injectionType + " is not supported.");
         }
     }
 
@@ -86,15 +95,15 @@ protected String testName(FrameworkMethod method) {
     @Override
     protected void validateConstructor(List<Throwable> errors) {
         validateOnlyOneConstructor(errors);
-        if (fieldsAreAnnotated()) {
+        if (getInjectionType() != InjectionType.CONSTRUCTOR) {
             validateZeroArgConstructor(errors);
         }
     }
 
     @Override
     protected void validateFields(List<Throwable> errors) {
         super.validateFields(errors);
-        if (fieldsAreAnnotated()) {
+        if (getInjectionType() == InjectionType.FIELD) {
             List<FrameworkField> annotatedFieldsByParameter = getAnnotatedFieldsByParameter();
             int[] usedIndices = new int[annotatedFieldsByParameter.size()];
             for (FrameworkField each : annotatedFieldsByParameter) {
@@ -137,6 +146,14 @@ private List<FrameworkField> getAnnotatedFieldsByParameter() {
         return getTestClass().getAnnotatedFields(Parameter.class);
     }
 
+    private InjectionType getInjectionType() {
+        if (fieldsAreAnnotated()) {
+            return InjectionType.FIELD;
+        } else {
+            return InjectionType.CONSTRUCTOR;
+        }
+    }
+
     private boolean fieldsAreAnnotated() {
         return !getAnnotatedFieldsByParameter().isEmpty();
     }