diff --git a/dvc/repo/diff.py b/dvc/repo/diff.py
index 354f0693b..9e0dfb7c0 100644
--- a/dvc/repo/diff.py
+++ b/dvc/repo/diff.py
@@ -105,7 +105,7 @@ def diff(self, target, a_ref=None, b_ref=None):
         string: string of output message with diff info
     """
     diff_dct = self.scm.diff(target, a_ref=a_ref, b_ref=b_ref)
-    msg = "dvc diff for '{}' from {} to {} \n\n".format(
+    msg = "dvc diff for '{}' from {} to {}\n\n".format(
         target, diff_dct["a_tag"], diff_dct["b_tag"]
     )
     if diff_dct["equal"]:
diff --git a/dvc/scm/base.py b/dvc/scm/base.py
index dc2dde69e..e2ae0ae36 100644
--- a/dvc/scm/base.py
+++ b/dvc/scm/base.py
@@ -17,6 +17,12 @@ class FileNotInRepoError(DvcException):
     """
 
 
+class FileNotInCommitError(DvcException):
+    """Thrown when trying to find a file/directory that is not
+    into the  specified commit in the repository
+    """
+
+
 class FileNotInTargetSubdirError(DvcException):
     """Thrown when trying to place .gitignore for a file that not in
     the file subdirectory."""
diff --git a/dvc/scm/git/__init__.py b/dvc/scm/git/__init__.py
index c1c93e00c..872bb247c 100644
--- a/dvc/scm/git/__init__.py
+++ b/dvc/scm/git/__init__.py
@@ -12,6 +12,7 @@ from dvc.scm.base import (
     SCMError,
     FileNotInRepoError,
     FileNotInTargetSubdirError,
+    FileNotInCommitError,
 )
 from dvc.scm.git.tree import GitTree
 import dvc.logger as logger
@@ -264,10 +265,10 @@ class Git(Base):
                     return None, commits
                 diff_obj = a_commit.diff(b_commit, paths=file_name)
         except (BadName, BadObject) as e:
-            raise SCMError(e)
+            raise SCMError("git problem", cause=e)
         if len(diff_obj) == 0:
             msg = "Have not found file/directory '{}' in the commits"
-            raise FileNotInRepoError(msg.format(file_name))
+            raise FileNotInCommitError(msg.format(file_name))
         return diff_obj[0], commits
 
     def _extract_fname(self, is_deleted, blob_obj):
diff --git a/tests/test_diff.py b/tests/test_diff.py
index 7037ce422..f9dfc960b 100644
--- a/tests/test_diff.py
+++ b/tests/test_diff.py
@@ -4,7 +4,7 @@ import os
 from dvc.main import main
 
 
-from dvc.scm.base import FileNotInRepoError
+from dvc.scm.base import FileNotInCommitError
 
 
 from tests.basic_env import TestDvc
@@ -29,9 +29,13 @@ class TestDiff(TestDvc):
 
 class TestDiffRepo(TestDiff):
     def test(self):
+        new_ref = self.git.head.commit
         msg = self.dvc.diff(self.new_file, a_ref=self.a_ref)
-        self.assertTrue("deleted file" in msg)
-        self.assertTrue(self.new_file in msg)
+        test_msg = "dvc diff for '{}' from ".format(self.new_file)
+        test_msg += "{} to {}\n\n".format(new_ref, self.a_ref)
+        test_msg += "-new_file with md5 25fa8325e4e0eb8180445e42558e60bd\n"
+        test_msg += "deleted file with size -8 Bytes"
+        self.assertEqual(test_msg, msg)
 
 
 class TestDiffCmdLine(TestDiff):
@@ -66,9 +70,15 @@ class TestDiffDir(TestDvc):
 
 class TestDiffDirRepo(TestDiffDir):
     def test(self):
+        new_ref = self.git.head.commit
         msg = self.dvc.diff(self.DATA_DIR, a_ref=self.a_ref)
-        self.assertTrue("1 file deleted" in msg, msg)
-        self.assertTrue("size was decreased by " in msg, msg)
+        test_msg = "dvc diff for '{}' from ".format(self.DATA_DIR)
+        test_msg += "{} to {}\n\n".format(new_ref, self.a_ref)
+        test_msg += "-data_dir with md5 d5782f3072167ad3a53ee80b92b30718\n"
+        test_msg += "+data_dir with md5 bff5a787d16460f32e9f2e62b183b1cc\n\n"
+        test_msg += "2 files didn't change, 0 files modified, 0 files added, "
+        test_msg += "1 file deleted, size was decreased by 30 Bytes"
+        self.assertEqual(msg, test_msg)
 
 
 class TestDiffFileNotFound(TestDiffDir):
@@ -77,22 +87,11 @@ class TestDiffFileNotFound(TestDiffDir):
         self.unknown_file = "unknown_file_" + str(id(self))
 
     def test(self):
-        with self.assertRaises(
-            FileNotInRepoError, msg="diff with incorrect arg"
-        ) as context:
+        with self.assertRaises(FileNotInCommitError):
             self.dvc.scm.diff(self.unknown_file, self.a_ref)
-        self.assertTrue(
-            "Have not found file/directory" in str(context.exception),
-            "scm raises with incorrect error message",
-        )
 
 
 class TestDiffFileNotFoundRepo(TestDiffFileNotFound):
     def test(self):
-        with self.assertRaises(
-            FileNotInRepoError, msg="diff with incorrect arg"
-        ) as context:
+        with self.assertRaises(FileNotInCommitError):
             self.dvc.diff(self.unknown_file, a_ref=self.a_ref)
-        self.assertTrue(
-            "Have not found file/directory" in str(context.exception)
-        )