Use object at least once before testing its label.

Otherwise my NVidia emits GL_INVALID_VALUE with message "that <object>
is not valid object", which isn't in the specs. I hate this "deferred
everything" approach in GL. Is this even legal optimization?

src/Magnum/Test/AbstractQueryGLTest.cpp

@@ -106,7 +106,15 @@ void AbstractQueryGLTest::label() {
        !Context::current()->isExtensionSupported<Extensions::GL::EXT::debug_label>())
         CORRADE_SKIP("Required extension is not available");
 
+    {
+        /** @todo Is this even legal optimization? */
+        CORRADE_EXPECT_FAIL("The object must be used at least once before setting/querying label.");
+        CORRADE_VERIFY(false);
+    }
     SampleQuery query;
+    query.begin(SampleQuery::Target::AnySamplesPassed);
+    query.end();
+
     CORRADE_COMPARE(query.label(), "");
 
     query.setLabel("MyQuery");

src/Magnum/Test/AbstractTextureGLTest.cpp

@@ -93,7 +93,14 @@ void AbstractTextureGLTest::label() {
        !Context::current()->isExtensionSupported<Extensions::GL::EXT::debug_label>())
         CORRADE_SKIP("Required extension is not available");
 
+    {
+        /** @todo Is this even legal optimization? */
+        CORRADE_EXPECT_FAIL("The object must be used at least once before setting/querying label.");
+        CORRADE_VERIFY(false);
+    }
     Texture2D texture;
+    texture.setMinificationFilter(Sampler::Filter::Linear);
+
     CORRADE_COMPARE(texture.label(), "");
 
     texture.setLabel("MyTexture");

src/Magnum/Test/BufferGLTest.cpp

@@ -118,7 +118,14 @@ void BufferGLTest::label() {
        !Context::current()->isExtensionSupported<Extensions::GL::EXT::debug_label>())
         CORRADE_SKIP("Required extension is not available");
 
+    {
+        /** @todo Is this even legal optimization? */
+        CORRADE_EXPECT_FAIL("The object must be used at least once before setting/querying label.");
+        CORRADE_VERIFY(false);
+    }
     Buffer buffer;
+    buffer.setData({nullptr, 3}, BufferUsage::StaticDraw);
+
     CORRADE_COMPARE(buffer.label(), "");
 
     buffer.setLabel("MyBuffer");

src/Magnum/Test/FramebufferGLTest.cpp

@@ -199,7 +199,19 @@ void FramebufferGLTest::label() {
        !Context::current()->isExtensionSupported<Extensions::GL::EXT::debug_label>())
         CORRADE_SKIP("Required extension is not available");
 
+    {
+        /** @todo Is this even legal optimization? */
+        CORRADE_EXPECT_FAIL("The object must be used at least once before setting/querying label.");
+        CORRADE_VERIFY(false);
+    }
+    Renderbuffer renderbuffer;
+    #ifndef MAGNUM_TARGET_GLES2
+    renderbuffer.setStorage(RenderbufferFormat::RGBA8, {128, 128});
+    #else
+    renderbuffer.setStorage(RenderbufferFormat::RGBA4, {128, 128});
+    #endif
     Framebuffer framebuffer({{}, Vector2i(32)});
+    framebuffer.attachRenderbuffer(Framebuffer::BufferAttachment(Framebuffer::BufferAttachment::Depth), renderbuffer);
 
     CORRADE_COMPARE(framebuffer.label(), "");
     MAGNUM_VERIFY_NO_ERROR();

src/Magnum/Test/MeshGLTest.cpp

@@ -295,7 +295,15 @@ void MeshGLTest::label() {
        !Context::current()->isExtensionSupported<Extensions::GL::EXT::debug_label>())
         CORRADE_SKIP("Required extension is not available");
 
+    {
+        /** @todo Is this even legal optimization? */
+        CORRADE_EXPECT_FAIL("The object must be used at least once before setting/querying label.");
+        CORRADE_VERIFY(false);
+    }
+    Buffer buffer{Buffer::Target::ElementArray};
     Mesh mesh;
+    mesh.setIndexBuffer(buffer, 0, Mesh::IndexType::UnsignedShort);
+
     CORRADE_COMPARE(mesh.label(), "");
 
     mesh.setLabel("MyMesh");

src/Magnum/Test/RenderbufferGLTest.cpp

@@ -116,7 +116,18 @@ void RenderbufferGLTest::label() {
        !Context::current()->isExtensionSupported<Extensions::GL::EXT::debug_label>())
         CORRADE_SKIP("Required extension is not available");
 
+    {
+        /** @todo Is this even legal optimization? */
+        CORRADE_EXPECT_FAIL("The object must be used at least once before setting/querying label.");
+        CORRADE_VERIFY(false);
+    }
     Renderbuffer renderbuffer;
+    #ifndef MAGNUM_TARGET_GLES2
+    renderbuffer.setStorage(RenderbufferFormat::RGBA8, {128, 128});
+    #else
+    renderbuffer.setStorage(RenderbufferFormat::RGBA4, {128, 128});
+    #endif
+
     CORRADE_COMPARE(renderbuffer.label(), "");
 
     renderbuffer.setLabel("MyRenderbuffer");