         
         describe("S3DXMLMTLDepthStencilDescriptorNode") {
             it("can parse a depth stencil descriptor") {
-                let desc = descMan.depthStencilDescriptors["depth_stencil_desc"]!
+                let desc = descMan.getDepthStencilDescriptor("depth_stencil_desc")
                 expect(desc.depthCompareFunction) == MTLCompareFunction.Never
                 expect(desc.depthWriteEnabled) == true
-                expect(desc.frontFaceStencil) == descMan.stencilDescriptors["stencil_desc"]
-                expect(desc.backFaceStencil) == descMan.stencilDescriptors["stencil_desc"]
+                expect(desc.frontFaceStencil) == descMan.getStencilDescriptor("stencil_desc")
+                expect(desc.backFaceStencil) == descMan.getStencilDescriptor("stencil_desc")
             }
         }
         
         describe("S3DXMLMTLRenderPipelineColorAttachmentDescriptorNode") {
             it("can parse a render pipeline color attachment descriptor") {
-                let desc = descMan.colorAttachmentDescriptors["color_attach_desc"]!
+                let desc = descMan.getColorAttachmentDescriptor("color_attach_desc")
                 expect(desc.blendingEnabled) == true
                 expect(desc.sourceRGBBlendFactor) == MTLBlendFactor.Zero
                 expect(desc.destinationRGBBlendFactor) == MTLBlendFactor.SourceColor


        describe("S3DXMLMTLVertexDescriptorNode") {
            it("can parse the attribute descriptor array") {
                let vertDesc = descMan.vertexDescriptors["common_vertex_desc"]!
                expect(vertDesc.attributes[0].format) == MTLVertexFormat.Float4
                expect(vertDesc.attributes[1].offset) == 16
            }
            
            it("can parse the buffer layout descriptor array") {
                let vertDesc = descMan.vertexDescriptors["common_vertex_desc"]!
                expect(vertDesc.layouts[0].stepFunction) == MTLVertexStepFunction.PerVertex
                expect(vertDesc.layouts[0].stride) == 48
                expect(vertDesc.layouts[0].stepRate) == 1

        
        describe("S3DXMLMTLRenderPassColorAttachmentDescriptorNode") {
            it("can parse a render pass color attachment descriptor") {
                let desc = descMan.getRenderPassColorAttachmentDescriptor("rpass_color_attach_desc")
                expect(desc.level) == 1
                expect(desc.slice) == 1
                expect(desc.depthPlane) == 1
