2 files changed, 128 insertions, 0 deletions

diff --git a/src/tests/CMakeLists.txt b/src/tests/CMakeLists.txt
index 348d1edf4..6a4022e45 100644
--- a/src/tests/CMakeLists.txt
+++ b/src/tests/CMakeLists.txt
@@ -8,6 +8,7 @@ add_executable(tests
     common/host_memory.cpp
     common/param_package.cpp
     common/ring_buffer.cpp
+    common/scratch_buffer.cpp
     common/unique_function.cpp
     core/core_timing.cpp
     core/internal_network/network.cpp
diff --git a/src/tests/common/scratch_buffer.cpp b/src/tests/common/scratch_buffer.cpp
new file mode 100644
index 000000000..a59490f55
--- /dev/null
+++ b/src/tests/common/scratch_buffer.cpp
@@ -0,0 +1,127 @@
+// SPDX-FileCopyrightText: Copyright 2022 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <algorithm>
+#include <array>
+#include <span>
+#include <catch2/catch.hpp>
+#include "common/common_types.h"
+#include "common/scratch_buffer.h"
+
+namespace Common {
+
+TEST_CASE("ScratchBuffer: Basic Test", "[common]") {
+    ScratchBuffer<u8> buf;
+
+    REQUIRE(buf.size() == 0U);
+    REQUIRE(buf.capacity() == 0U);
+
+    std::array<u8, 10> payload;
+    payload.fill(66);
+
+    buf.resize(payload.size());
+    REQUIRE(buf.size() == payload.size());
+    REQUIRE(buf.capacity() == payload.size());
+
+    std::memcpy(buf.data(), payload.data(), payload.size());
+    for (size_t i = 0; i < payload.size(); ++i) {
+        REQUIRE(buf[i] == payload[i]);
+    }
+}
+
+TEST_CASE("ScratchBuffer: Resize Grow", "[common]") {
+    std::array<u8, 10> payload;
+    payload.fill(66);
+
+    ScratchBuffer<u8> buf(payload.size());
+    REQUIRE(buf.size() == payload.size());
+    REQUIRE(buf.capacity() == payload.size());
+
+    // Increasing the size should reallocate the buffer
+    buf.resize(payload.size() * 2);
+    REQUIRE(buf.size() == payload.size() * 2);
+    REQUIRE(buf.capacity() == payload.size() * 2);
+
+    // Since the buffer is not value initialized, reading its data will be garbage
+}
+
+TEST_CASE("ScratchBuffer: Resize Shrink", "[common]") {
+    std::array<u8, 10> payload;
+    payload.fill(66);
+
+    ScratchBuffer<u8> buf(payload.size());
+    REQUIRE(buf.size() == payload.size());
+    REQUIRE(buf.capacity() == payload.size());
+
+    std::memcpy(buf.data(), payload.data(), payload.size());
+    for (size_t i = 0; i < payload.size(); ++i) {
+        REQUIRE(buf[i] == payload[i]);
+    }
+
+    // Decreasing the size should not cause a buffer reallocation
+    // This can be tested by ensuring the buffer capacity and data has not changed,
+    buf.resize(1U);
+    REQUIRE(buf.size() == 1U);
+    REQUIRE(buf.capacity() == payload.size());
+
+    for (size_t i = 0; i < payload.size(); ++i) {
+        REQUIRE(buf[i] == payload[i]);
+    }
+}
+
+TEST_CASE("ScratchBuffer: Span Size", "[common]") {
+    std::array<u8, 10> payload;
+    payload.fill(66);
+
+    ScratchBuffer<u8> buf(payload.size());
+    REQUIRE(buf.size() == payload.size());
+    REQUIRE(buf.capacity() == payload.size());
+
+    std::memcpy(buf.data(), payload.data(), payload.size());
+    for (size_t i = 0; i < payload.size(); ++i) {
+        REQUIRE(buf[i] == payload[i]);
+    }
+
+    buf.resize(3U);
+    REQUIRE(buf.size() == 3U);
+    REQUIRE(buf.capacity() == payload.size());
+
+    const auto buf_span = std::span<u8>(buf);
+    // The span size is the last requested size of the buffer, not its capacity
+    REQUIRE(buf_span.size() == buf.size());
+
+    for (size_t i = 0; i < buf_span.size(); ++i) {
+        REQUIRE(buf_span[i] == buf[i]);
+        REQUIRE(buf_span[i] == payload[i]);
+    }
+}
+
+TEST_CASE("ScratchBuffer: Span Writes", "[common]") {
+    std::array<u8, 10> payload;
+    payload.fill(66);
+
+    ScratchBuffer<u8> buf(payload.size());
+    REQUIRE(buf.size() == payload.size());
+    REQUIRE(buf.capacity() == payload.size());
+
+    std::memcpy(buf.data(), payload.data(), payload.size());
+    for (size_t i = 0; i < payload.size(); ++i) {
+        REQUIRE(buf[i] == payload[i]);
+    }
+
+    buf.resize(3U);
+    REQUIRE(buf.size() == 3U);
+    REQUIRE(buf.capacity() == payload.size());
+
+    const auto buf_span = std::span<u8>(buf);
+    REQUIRE(buf_span.size() == buf.size());
+
+    for (size_t i = 0; i < buf_span.size(); ++i) {
+        const auto new_value = static_cast<u8>(i + 1U);
+        // Writes to a span of the scratch buffer will propogate to the buffer itself
+        buf_span[i] = new_value;
+        REQUIRE(buf[i] == new_value);
+    }
+}
+
+} // namespace Common