Moved control images one per directory and updated render checker to generate paths and filenames more cleanly. All tests pass for me.

tests/src/core/qgsrenderchecker.cpp

@@ -43,6 +43,13 @@ QString QgsRenderChecker::controlImagePath() const
   return myControlImageDir;
 }
 
+void QgsRenderChecker::setControlName(const QString theName)
+{
+  mControlName = theName;
+  mExpectedImageFile = controlImagePath() + theName + QDir::separator() +
+      theName + ".png";
+}
+
 bool QgsRenderChecker::runTest( QString theTestName,
                                 unsigned int theMismatchCount )
 {

tests/src/core/qgsrenderchecker.h

@@ -44,7 +44,11 @@ public:
   //only records time for actual render part
   int elapsedTime() { return mElapsedTime; };
   void setElapsedTimeTarget(int theTarget) { mElapsedTimeTarget = theTarget; };
-  void setExpectedImage (QString theImageFileName) { mExpectedImageFile = theImageFileName; };
+  /** Base directory name for the control image (with control image path
+    * suffixed) the path to the image will be constructed like this:
+    * controlImagePath + '/' + mControlName + '/' + mControlName + '.png'
+    */
+  void setControlName(const QString theName);
   void setRenderedImage (QString theImageFileName) { mRenderedImageFile = theImageFileName; };
   void setMapRenderer ( QgsMapRenderer *  thepMapRenderer) { mpMapRenderer = thepMapRenderer; };
   /**
@@ -73,6 +77,7 @@ public:
 private:
   QString mReport;
   QString mExpectedImageFile;
+  QString mControlName;
   QString mRenderedImageFile; 
   unsigned int mMismatchCount;
   unsigned int mMatchTarget;

tests/src/core/regression992.cpp

@@ -106,8 +106,7 @@ void Regression992::regression992()
   QVERIFY( mpRasterLayer->isValid() );
   mpMapRenderer->setExtent( mpRasterLayer->extent() );
   QgsRenderChecker myChecker;
-  myChecker.setExpectedImage( myChecker.controlImagePath() +
-                              "expected_rgbwcmyk01_YeGeo.jp2.png" );
+  myChecker.setControlName( "expected_rgbwcmyk01_YeGeo.jp2" );
   myChecker.setMapRenderer( mpMapRenderer );
   // allow up to 300 mismatched pixels
   bool myResultFlag = myChecker.runTest( "regression992", 300 );

tests/src/core/testqgsgeometry.cpp

@@ -314,8 +314,7 @@ bool TestQgsGeometry::renderCheck( QString theTestName, QString theComment )
   QString myFileName = myTmpDir + theTestName + ".png";
   mImage.save( myFileName, "PNG" );
   QgsRenderChecker myChecker;
-  myChecker.setExpectedImage( myChecker.controlImagePath() +
-                              "expected_" + theTestName + ".png" );
+  myChecker.setControlName( "expected_" + theTestName );
   myChecker.setRenderedImage( myFileName );
   bool myResultFlag = myChecker.compareImages( theTestName );
   mReport += myChecker.report();

tests/src/core/testqgsmaprenderer.cpp

@@ -193,8 +193,7 @@ void TestQgsMapRenderer::performanceTest()
 {
   mpMapRenderer->setExtent( mpPolysLayer->extent() );
   QgsRenderChecker myChecker;
-  myChecker.setExpectedImage(
-        myChecker.controlImagePath() + "expected_maprender.png" );
+  myChecker.setControlName( "expected_maprender" );
   myChecker.setMapRenderer( mpMapRenderer );
   bool myResultFlag = myChecker.runTest( "maprender" );
   mReport += myChecker.report();

tests/src/core/testqgsrasterlayer.cpp

@@ -256,8 +256,7 @@ bool TestQgsRasterLayer::render( QString theTestType )
 {
   mReport += "<h2>" + theTestType + "</h2>\n";
   QgsRenderChecker myChecker;
-  myChecker.setExpectedImage( myChecker.controlImagePath()
-                              + "expected_" + theTestType + ".png" );
+  myChecker.setControlName( "expected_" + theTestType );
   myChecker.setMapRenderer( mpMapRenderer );
   bool myResultFlag = myChecker.runTest( theTestType );
   mReport += "\n\n\n" + myChecker.report();

tests/src/core/testqgsrenderers.cpp

@@ -216,9 +216,7 @@ bool TestQgsRenderers::imageCheck( QString theTestType )
   //ensure the rendered output matches our control image
   mpMapRenderer->setExtent( mpPointsLayer->extent() );
   QgsRenderChecker myChecker;
-  QString myExpectedImage = myChecker.controlImagePath() +
-      "expected_" + theTestType + ".png";
-  myChecker.setExpectedImage( myExpectedImage );
+  myChecker.setControlName( "expected_" + theTestType );
   myChecker.setMapRenderer( mpMapRenderer );
   bool myResultFlag = myChecker.runTest( theTestType );
   mReport += myChecker.report();

tests/testdata/control_images/expected_raster/expected_raster.png.aux.xml

@@ -0,0 +1,13 @@
+<PAMDataset>
+  <Metadata domain="IMAGE_STRUCTURE">
+    <MDI key="INTERLEAVE">PIXEL</MDI>
+  </Metadata>
+  <PAMRasterBand band="1">
+    <Metadata>
+      <MDI key="STATISTICS_MINIMUM">0</MDI>
+      <MDI key="STATISTICS_MAXIMUM">255</MDI>
+      <MDI key="STATISTICS_MEAN">127.2</MDI>
+      <MDI key="STATISTICS_STDDEV">81.364365664583</MDI>
+    </Metadata>
+  </PAMRasterBand>
+</PAMDataset>