fix metrics tests on windows

tests/test_metrics.py

@@ -378,10 +378,26 @@ class TestCachedMetrics(TestDvc):
         self.dvc.scm.checkout(branch)
         self.dvc.checkout(force=True)
 
-        content = json.dumps({"metrics": branch})
+        print(
+            'print(json.dumps({{"metrics": "{branch}"}})\n'.format(
+                branch=branch
+            )
+        )
+
+        with open("code.py", "w+") as fobj:
+            fobj.write("import sys\n")
+            fobj.write("import os\n")
+            fobj.write("import json\n")
+            fobj.write(
+                'print(json.dumps({{"metrics": "{branch}"}}))\n'.format(
+                    branch=branch
+                )
+            )
+
         stage = self.dvc.run(
+            deps=["code.py"],
             metrics=["metrics.json"],
-            cmd="echo '{content}' > metrics.json".format(content=content),
+            cmd="python code.py metrics.json > metrics.json",
         )
         self.assertIsNotNone(stage)
         self.assertEqual(stage.relpath, "metrics.json.dvc")

tests/test_run.py

@@ -532,18 +532,14 @@ class TestCmdRunOverwrite(TestDvc):
 
 class TestCmdRunCliMetrics(TestDvc):
     def test_cached(self):
-        ret = main(
-            ["run", "-m", "metrics.txt", "echo -n 'test' > metrics.txt"]
-        )
+        ret = main(["run", "-m", "metrics.txt", "echo 'test' > metrics.txt"])
         self.assertEqual(ret, 0)
-        self.assertEqual(open("metrics.txt", "r").read(), "test")
+        self.assertEqual(open("metrics.txt", "r").read().rstrip(), "test")
 
     def test_not_cached(self):
-        ret = main(
-            ["run", "-M", "metrics.txt", "echo -n 'test' > metrics.txt"]
-        )
+        ret = main(["run", "-M", "metrics.txt", "echo 'test' > metrics.txt"])
         self.assertEqual(ret, 0)
-        self.assertEqual(open("metrics.txt", "r").read(), "test")
+        self.assertEqual(open("metrics.txt", "r").read().rstrip(), "test")
 
 
 class TestRunDeterministicBase(TestDvc):