chore: import upstream snapshot with attribution

test/op/UnstackTest.cpp

@@ -0,0 +1,42 @@
+//
+//  UnstackTest.cpp
+//  MNNTests
+//
+//  Created by MNN on 2019/12/18.
+//  Copyright © 2018, Alibaba Group Holding Limited
+//
+
+#include <MNN/expr/Expr.hpp>
+#include <MNN/expr/ExprCreator.hpp>
+#include "MNNTestSuite.h"
+#include "TestUtils.h"
+
+using namespace MNN::Express;
+class UnstackTest : public MNNTestCase {
+public:
+    virtual ~UnstackTest() = default;
+    virtual bool run(int precision) {
+        auto input = _Input({3, 1, 2, 2}, NCHW);
+        input->setName("input_tensor");
+        // set input data
+        const float inpudata[] = {1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0};
+        auto inputPtr          = input->writeMap<float>();
+        memcpy(inputPtr, inpudata, 12 * sizeof(float));
+        input->unMap();
+        auto outputs                              = _Unstack(input, -2);
+        const std::vector<float> expectedOutput_0 = {1.0, 2.0, 5.0, 6.0, 9.0, 10.0};
+        const std::vector<float> expectedOutput_1 = {3.0, 4.0, 7.0, 8.0, 11.0, 12.0};
+        auto gotOutput_0                          = outputs[0]->readMap<float>();
+        auto gotOutput_1                          = outputs[1]->readMap<float>();
+        if (!checkVector<float>(gotOutput_0, expectedOutput_0.data(), 6, 0.01)) {
+            MNN_ERROR("UnstackTest test failed!\n");
+            return false;
+        }
+        if (!checkVector<float>(gotOutput_1, expectedOutput_1.data(), 6, 0.01)) {
+            MNN_ERROR("UnstackTest test failed!\n");
+            return false;
+        }
+        return true;
+    }
+};
+MNNTestSuiteRegister(UnstackTest, "op/unstack");