diff --git a/aos/sha256_test.cc b/aos/sha256_test.cc
new file mode 100644
index 0000000..33ab5ec
--- /dev/null
+++ b/aos/sha256_test.cc
@@ -0,0 +1,27 @@
+#include "aos/sha256.h"
+
+#include "gtest/gtest.h"
+
+#include "aos/testing/tmpdir.h"
+#include "aos/util/file.h"
+
+namespace aos::testing {
+
+constexpr const char *kTestString = "Test String";
+constexpr const char *kTestStringSha =
+    "30c6ff7a44f7035af933babaea771bf177fc38f06482ad06434cbcc04de7ac14";
+
+TEST(Sha256Test, ChecksumString) {
+  EXPECT_EQ(kTestStringSha, Sha256(kTestString));
+  EXPECT_EQ("2b4da12a4bfe66a061c24440521a9e5b994e4f0bcc47a17436275f5283bb6852",
+            Sha256("Test String 2"));
+}
+
+TEST(Sha256Test, ChecksumFile) {
+  const std::filesystem::path test_file =
+      aos::testing::TestTmpDir() + "/test.txt";
+  util::WriteStringToFileOrDie(test_file.string(), kTestString);
+  EXPECT_EQ(kTestStringSha, Sha256OfFile(test_file));
+}
+
+}  // namespace aos::testing