1 files changed, 54 insertions, 0 deletions
diff --git a/app/src/test/java/invalid/lena/scrcpy/AtomicFilesTest.java b/app/src/test/java/invalid/lena/scrcpy/AtomicFilesTest.java
new file mode 100644
index 0000000..7124fd2
--- /dev/null
+++ b/app/src/test/java/invalid/lena/scrcpy/AtomicFilesTest.java
@@ -0,0 +1,54 @@
+package invalid.lena.scrcpy;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertFalse;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.File;
+import java.nio.file.Files;
+
+public class AtomicFilesTest {
+
+    @Rule
+    public TemporaryFolder dir = new TemporaryFolder();
+
+    @Test
+    public void writeCreatesFile() throws Exception {
+        File f = new File(dir.getRoot(), "x");
+        AtomicFiles.write(f, "hello".getBytes());
+        assertArrayEquals("hello".getBytes(), Files.readAllBytes(f.toPath()));
+    }
+
+    @Test
+    public void writeReplacesExistingWhole() throws Exception {
+        File f = new File(dir.getRoot(), "x");
+        AtomicFiles.write(f, "old".getBytes());
+        AtomicFiles.write(f, "new-and-longer".getBytes());
+        assertArrayEquals("new-and-longer".getBytes(), Files.readAllBytes(f.toPath()));
+    }
+
+    @Test
+    public void writeLeavesNoTempBehind() throws Exception {
+        File f = new File(dir.getRoot(), "x");
+        AtomicFiles.write(f, "data".getBytes());
+        assertFalse(new File(dir.getRoot(), "x.tmp").exists());
+    }
+
+    @Test
+    public void staleTempDoesNotCorruptDestination() throws Exception {
+        // A crash after staging but before the rename leaves a partial ".tmp".
+        // The destination must still hold the previous good content, and the
+        // next successful write must overwrite the stale temp cleanly.
+        File f = new File(dir.getRoot(), "x");
+        AtomicFiles.write(f, "good".getBytes());
+        Files.write(new File(dir.getRoot(), "x.tmp").toPath(), "partial".getBytes());
+        assertArrayEquals("good".getBytes(), Files.readAllBytes(f.toPath()));
+
+        AtomicFiles.write(f, "good2".getBytes());
+        assertArrayEquals("good2".getBytes(), Files.readAllBytes(f.toPath()));
+        assertFalse(new File(dir.getRoot(), "x.tmp").exists());
+    }
+}