Added required attribute to ScenarioState.

This commit adds a new boolean attribute "required" to both
ScenarioState and ExpectedScenarioState. If set to true on a
field within a stage, corresponding tests will fail automatically
if the state hasn't been provided.

fixes TNG#255

jgiven-core/src/main/java/com/tngtech/jgiven/annotation/ExpectedScenarioState.java

@@ -18,4 +18,10 @@
 @Target( ElementType.FIELD )
 public @interface ExpectedScenarioState {
     Resolution resolution() default Resolution.AUTO;
+
+    /**
+     * Defines whether this state is required.
+     * If set to {@code true} and no stage provided this state, the tests will automatically fail.
+     */
+    boolean required() default false;
 }

jgiven-core/src/main/java/com/tngtech/jgiven/annotation/ScenarioState.java

@@ -18,4 +18,10 @@
     public enum Resolution {
         TYPE, NAME, AUTO;
     }
+
+    /**
+     * Defines whether this state is required.
+     * If set to {@code true} and no stage provided this state, the tests will automatically fail.
+     */
+    boolean required() default false;
 }

jgiven-core/src/main/java/com/tngtech/jgiven/impl/inject/ValueInjector.java

@@ -90,6 +90,8 @@ public void updateValues( Object object ) {
                 if( value != null ) {
                     field.set( object, value );
                     log.debug( "Setting field {} to value {}", field, value );
+                } else if( isRequired( field ) ) {
+                    throw new RuntimeException( "TODO Better exception?" );
                 }
             } catch( IllegalAccessException e ) {
                 throw new RuntimeException( "Error while updating field " + field, e );
@@ -107,23 +109,19 @@ public <T> void injectValueByName( String name, T value ) {
 
     private void updateValue( Field field, Object value ) {
         Resolution resolution = getResolution( field );
-        Class<?> type = field.getType();
         if( resolution == Resolution.NAME ) {
-            String name = field.getName();
-            state.updateValueByName( name, value );
+            state.updateValueByName( field.getName(), value );
         } else {
-            state.updateValueByType( type, value );
+            state.updateValueByType( field.getType(), value );
         }
     }
 
     private Object getValue( Field field ) {
         Resolution resolution = getResolution( field );
-        Class<?> type = field.getType();
         if( resolution == Resolution.NAME ) {
-            String name = field.getName();
-            return state.getValueByName( name );
+            return state.getValueByName( field.getName() );
         }
-        return state.getValueByType( type );
+        return state.getValueByType( field.getType() );
     }
 
     private Resolution getResolution( Field field ) {
@@ -146,9 +144,23 @@ private Resolution getDeclaredResolution( Field field ) {
                 return ( (ExpectedScenarioState) annotation ).resolution();
             }
         }
+
         throw new IllegalArgumentException( "Field " + field + " has no valid annotation" );
     }
 
+    private boolean isRequired( Field field ) {
+        for( Annotation annotation : field.getAnnotations() ) {
+            if( annotation instanceof ScenarioState ) {
+                return ( (ScenarioState) annotation ).required();
+            }
+            if( annotation instanceof ExpectedScenarioState ) {
+                return ( (ExpectedScenarioState) annotation ).required();
+            }
+        }
+
+        return false;
+    }
+
     private boolean typeIsTooGeneric( Class<?> type ) {
         return type.isPrimitive()
                 || type.getName().startsWith( "java.lang" )

jgiven-junit/src/test/java/com/tngtech/jgiven/junit/ScenarioExecutionTest.java

@@ -352,4 +352,17 @@ public void abstract_steps_should_appear_in_the_report_model() throws Throwable
 
     }
 
+    static class StageWithMissingState {
+        @ScenarioState( required = true )
+        Boolean willNotBeProvided;
+
+        public void something() {}
+    }
+
+    @Test( expected = RuntimeException.class )
+    public void required_states_must_be_present() throws Throwable {
+        StageWithMissingState stage = addStage( StageWithMissingState.class );
+        stage.something();
+    }
+
 }