tests: add result examples

dvc/command/diff.py

@@ -35,7 +35,7 @@ def add_parser(subparsers, parent_parser):
         "a_ref",
         help="Git reference from which diff calculates (defaults to HEAD)",
         nargs="?",
-        default="HEAD"
+        default="HEAD",
     )
     diff_parser.add_argument(
         "b_ref",

tests/func/test_diff.py

@@ -10,21 +10,60 @@ def test_no_scm(tmp_dir, dvc):
 def test_added(tmp_dir, scm, dvc):
     tmp_dir.dvc_gen("file", "text")
 
-    pytest.skip("TODO: define output structure")
+    result = {
+        "old": [],
+        "new": [
+            {
+                "filename": "file",
+                "checksum": "1cb251ec0d568de6a929b520c4aed8d1",
+                "size": 4,
+            }
+        ],
+    }
+
+    assert result == dvc.diff()
 
 
 def test_deleted(tmp_dir, scm, dvc):
     tmp_dir.dvc_gen("file", "text", commit="add file")
     (tmp_dir / "file").unlink()
 
-    pytest.skip("TODO: define output structure")
+    result = {
+        "old": [
+            {
+                "filename": "file",
+                "checksum": "1cb251ec0d568de6a929b520c4aed8d1",
+                "size": 4,
+            }
+        ],
+        "new": [],
+    }
+
+    assert result == dvc.diff()
 
 
 def test_modified(tmp_dir, scm, dvc):
     tmp_dir.dvc_gen("file", "first", commit="first version")
     tmp_dir.dvc_gen("file", "second")
 
-    pytest.skip("TODO: define output structure")
+    result = {
+        "old": [
+            {
+                "filename": "file",
+                "checksum": "8b04d5e3775d298e78455efc5ca404d5",
+                "size": 6,
+            }
+        ],
+        "new": [
+            {
+                "filename": "file",
+                "checksum": "a9f0e61a137d86aa9db53465e0801612",
+                "size": 6,
+            }
+        ],
+    }
+
+    assert result == dvc.diff()
 
 
 def test_refs(tmp_dir, scm, dvc):