Add ValidationTest and an example validation test.

Validation tests are tests of the backend state-tracking and validation
code that don't require a GPU as they are running on the null backend.
This commit adds a very simple (and almost useless) BufferValidationTest
as an example of a validation test.

src/tests/unittests/validation/ValidationTest.cpp

@@ -0,0 +1,70 @@
+// Copyright 2017 The NXT Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "ValidationTest.h"
+
+#include "nxt/nxt.h"
+
+namespace backend {
+    namespace null {
+        void Init(nxtProcTable* procs, nxtDevice* device);
+    }
+}
+
+ValidationTest::ValidationTest() {
+    nxtProcTable procs;
+    nxtDevice cDevice;
+    backend::null::Init(&procs, &cDevice);
+
+    nxtSetProcs(&procs);
+    device = nxt::Device::Acquire(cDevice);
+}
+
+ValidationTest::~ValidationTest() {
+    // We need to destroy NXT objects before setting the procs to null otherwise the nxt*Release
+    // will call a nullptr
+    device = nxt::Device();
+    nxtSetProcs(nullptr);
+}
+
+void ValidationTest::TearDown() {
+    for (auto& expectation : expectations) {
+        std::string name = expectation.debugName;
+        if (name.empty()) {
+            name = "<no debug name set>";
+        }
+
+        ASSERT_TRUE(expectation.gotStatus) << "Didn't get a status for " << name;
+
+        ASSERT_NE(NXT_BUILDER_ERROR_STATUS_UNKNOWN, expectation.gotStatus) << "Got unknown status for " << name;
+
+        bool wasSuccess = expectation.status == NXT_BUILDER_ERROR_STATUS_SUCCESS;
+        ASSERT_EQ(expectation.expectSuccess, wasSuccess)
+            << "Got wrong status value for " << name
+            << ", status was " << expectation.status << " with \"" << expectation.statusMessage << "\"";
+    }
+}
+
+void ValidationTest::OnBuilderErrorStatus(nxtBuilderErrorStatus status, const char* message, nxt::CallbackUserdata userdata1, nxt::CallbackUserdata userdata2) {
+    auto* self = reinterpret_cast<ValidationTest*>(static_cast<uintptr_t>(userdata1));
+    size_t index = userdata2;
+
+    ASSERT_LT(index, self->expectations.size());
+
+    auto& expectation = self->expectations[index];
+    ASSERT_FALSE(expectation.gotStatus);
+    expectation.gotStatus = true;
+    expectation.status = status;
+    expectation.statusMessage = message;
+}