test: ensure render pipelines have at least 1 target

tests/tests/pipeline.rs

@@ -35,3 +35,46 @@ static PIPELINE_DEFAULT_LAYOUT_BAD_MODULE: GpuTestConfiguration = GpuTestConfigu
             pipeline.get_bind_group_layout(0);
         });
     });
+
+const TRIVIAL_VERTEX_SHADER_DESC: wgpu::ShaderModuleDescriptor = wgpu::ShaderModuleDescriptor {
+    label: Some("trivial vertex shader"),
+    source: wgpu::ShaderSource::Wgsl(std::borrow::Cow::Borrowed(
+        "@vertex fn main() -> @builtin(position) vec4<f32> { return vec4<f32>(0); }",
+    )),
+};
+
+#[gpu_test]
+static NO_TARGETLESS_RENDER: GpuTestConfiguration = GpuTestConfiguration::new()
+    .parameters(TestParameters::default())
+    .run_sync(|ctx| {
+        fail(&ctx.device, || {
+            // Testing multisampling is important, because some backends don't behave well if one
+            // tries to compile code in an unsupported multisample count. Failing to validate here
+            // has historically resulted in requesting the back end to compile code.
+            for power_of_two in [1, 2, 4, 8, 16, 32, 64] {
+                ctx.device
+                    .create_render_pipeline(&wgpu::RenderPipelineDescriptor {
+                        label: None,
+                        layout: None,
+                        vertex: wgpu::VertexState {
+                            module: &ctx.device.create_shader_module(TRIVIAL_VERTEX_SHADER_DESC),
+                            entry_point: "main",
+                            compilation_options: Default::default(),
+                            buffers: &[],
+                        },
+                        primitive: Default::default(),
+                        depth_stencil: None,
+                        multisample: wgpu::MultisampleState {
+                            count: power_of_two,
+                            ..Default::default()
+                        },
+                        fragment: None,
+                        multiview: None,
+                        cache: None,
+                    });
+            }
+        })
+        // TODO: concrete error message:
+        // At least one color attachment or depth-stencil attachment was expected, but no
+        // render target for the pipeline was specified.
+    });