Add tests for comparison of file contents

tests/test-data/cores.txt

@@ -0,0 +1 @@
+2

tests/test_compare.py

@@ -1,11 +1,20 @@
 import unittest
 from cwltest import CompareFail
-from cwltest.utils import compare_file
+from cwltest.utils import compare_file, compare
 
 
-class TestCompareFile(unittest.TestCase):
+class TestCompare(unittest.TestCase):
 
-    def test_general(self):
+    def compare_success(self, expected, actual):
+        try:
+            compare(expected, actual)
+        except CompareFail:
+            self.fail("Comparison failed unexpectedly")
+
+
+class TestCompareFile(TestCompare):
+
+    def test_compare_file(self):
         expected = {
             "location": "cores.txt",
             "size": 2,
@@ -21,8 +30,44 @@ def test_general(self):
             "path": "/var/folders/8x/2df05_7j20j6r8y81w4qf43r0000gn/T/tmpG0EkrS/cores.txt",
             "size": 2
         }
-
         try:
             compare_file(expected, actual)
         except CompareFail:
-            self.fail("File comparison failed unexpectedly")
+            self.fail("File comparison failed unexpectedly")
+
+    def test_compare_contents_success(self):
+        expected = {
+            "location": "cores.txt",
+            "size": 2,
+            "class": "File",
+            "contents": "2\n"
+        }
+
+        actual = {
+            "basename": "cores.txt",
+            "checksum": "sha1$7448d8798a4380162d4b56f9b452e2f6f9e24e7a",
+            "class": "File",
+            "location": "file:///var/folders/8x/2df05_7j20j6r8y81w4qf43r0000gn/T/tmpG0EkrS/cores.txt",
+            "path": "tests/test-data/cores.txt",
+            "size": 2
+        }
+        self.compare_success(expected, actual)
+
+    def test_compare_contents_failure(self):
+        expected = {
+            "location": "cores.txt",
+            "size": 2,
+            "class": "File",
+            "contents": "2"
+        }
+
+        actual = {
+            "basename": "cores.txt",
+            "checksum": "sha1$7448d8798a4380162d4b56f9b452e2f6f9e24e7a",
+            "class": "File",
+            "location": "file:///var/folders/8x/2df05_7j20j6r8y81w4qf43r0000gn/T/tmpG0EkrS/cores.txt",
+            "path": "tests/test-data/cores.txt",
+            "size": 2
+        }
+        with self.assertRaises(CompareFail):
+            compare_file(expected, actual)