diff --git a/test/fd/atomic.cpp b/test/fd/atomic.cpp
new file mode 100644
index 0000000..c67ce41
--- /dev/null
+++ b/test/fd/atomic.cpp
@@ -0,0 +1,71 @@
+#include <filesystem>
+#include <memory>
+#include <stdplus/fd/atomic.hpp>
+#include <stdplus/fd/ops.hpp>
+#include <stdplus/gtest/tmp.hpp>
+#include <string_view>
+
+namespace stdplus
+{
+namespace fd
+{
+
+using std::literals::string_view_literals::operator""sv;
+
+class AtomicWriterTest : public gtest::TestWithTmp
+{
+  protected:
+    std::string filename;
+    std::unique_ptr<AtomicWriter> file;
+
+    AtomicWriterTest() : filename(fmt::format("{}/out", CaseTmpDir()))
+    {
+    }
+
+    ~AtomicWriterTest() noexcept
+    {
+        if (file)
+        {
+            auto tmpname = file->getTmpname();
+            file.reset();
+            if (!tmpname.empty())
+            {
+                EXPECT_FALSE(std::filesystem::exists(tmpname));
+            }
+        }
+    }
+};
+
+TEST_F(AtomicWriterTest, NoCommit)
+{
+    ASSERT_NO_THROW(file = std::make_unique<AtomicWriter>(filename, 0644));
+    writeExact(*file, "hi\n"sv);
+    EXPECT_FALSE(std::filesystem::exists(filename));
+    EXPECT_TRUE(std::filesystem::exists(file->getTmpname()));
+}
+
+TEST_F(AtomicWriterTest, BadCommit)
+{
+    auto tmp = fmt::format("{}/tmp.XXXXXX", CaseTmpDir());
+    ASSERT_NO_THROW(file =
+                        std::make_unique<AtomicWriter>("/dev/null", 0644, tmp));
+    writeExact(*file, "hi\n"sv);
+    EXPECT_TRUE(std::filesystem::exists(file->getTmpname()));
+    EXPECT_THROW(file->commit(), std::filesystem::filesystem_error);
+    EXPECT_EQ(file->getTmpname(), ""sv);
+}
+
+TEST_F(AtomicWriterTest, Basic)
+{
+    ASSERT_NO_THROW(file = std::make_unique<AtomicWriter>(filename, 0644));
+    writeExact(*file, "hi\n"sv);
+    EXPECT_TRUE(std::filesystem::exists(file->getTmpname()));
+    EXPECT_NO_THROW(file->commit());
+    EXPECT_EQ(file->getTmpname(), ""sv);
+    std::error_code ec;
+    EXPECT_EQ(3, std::filesystem::file_size(filename, ec));
+    EXPECT_EQ(std::errc{}, ec);
+}
+
+} // namespace fd
+} // namespace stdplus