test: Add test for diff command functionality

src/tests.rs

@@ -256,4 +256,59 @@ mod tests {
             //assert!(!output.status.success(), "Command succeded when it should have failed: {}  RC={}", cmd, output.status);
         });
     }
+
+    // Test: Diff two items and verify the output
+    #[test]
+    fn test_diff_items() {
+        with_temp_env(|data_dir| {
+            // Create test items with the common environment setup
+            create_test_items(data_dir);
+
+            let env = format!("KEEP_DIR={} cargo run --", data_dir.display());
+
+            let cmd = format!("{} --diff 1 2", env);
+            let output = run_sh(cmd.as_str());
+            assert!(
+                output.status.success(),
+                "Command failed: {}  RC={}",
+                cmd,
+                output.status
+            );
+            assert!(String::from_utf8_lossy(&output.stdout).contains("test content A"));
+            assert!(String::from_utf8_lossy(&output.stdout).contains("test content B"));
+
+            let cmd = format!("{} --diff tag_a tag_b", env);
+            let output = run_sh(cmd.as_str());
+            assert!(
+                output.status.success(),
+                "Command failed: {}  RC={}",
+                cmd,
+                output.status
+            );
+            assert!(String::from_utf8_lossy(&output.stdout).contains("test content A"));
+            assert!(String::from_utf8_lossy(&output.stdout).contains("test content B"));
+
+            let cmd = format!("{} --diff tag_a 2", env);
+            let output = run_sh(cmd.as_str());
+            assert!(
+                output.status.success(),
+                "Command failed: {}  RC={}",
+                cmd,
+                output.status
+            );
+            assert!(String::from_utf8_lossy(&output.stdout).contains("test content A"));
+            assert!(String::from_utf8_lossy(&output.stdout).contains("test content B"));
+
+            let cmd = format!("{} --diff 9999 2", env);
+            let output = run_sh(cmd.as_str());
+            assert!(
+                output.status.success(),
+                "Command failed: {}  RC={}",
+                cmd,
+                output.status
+            );
+            // Output should be empty for non-existent item
+            assert!(String::from_utf8_lossy(&output.stdout).is_empty());
+        });
+    }
 }