Improve UX and tests of check command

This should really be 3 atomic commits but I'm short on time.

- Prints a message on clean environment
- Marked tests as network based
- Added helper that matches lines irrespective of order.

pip/commands/check.py

@@ -35,3 +35,5 @@ class CheckCommand(Command):
 
         if missing_reqs_dict or incompatible_reqs_dict:
             return 1
+        else:
+            logger.info("No broken requirements found.")

tests/functional/test_check.py

@@ -1,11 +1,26 @@
+import pytest
+
+
+def matches_expected_lines(string, expected_lines):
+    # Ignore empty lines
+    output_lines = set(filter(None, string.splitlines()))
+    # Match regardless of order
+    return set(output_lines) == set(expected_lines)
+
+
 def test_check_clean(script):
-    """On a clean environment, check shouldn't return anything.
+    """On a clean environment, check should print a helpful message.
 
     """
     result = script.pip('check')
-    assert result.stdout == ""
+
+    expected_lines = (
+        "No broken requirements found.",
+    )
+    assert matches_expected_lines(result.stdout, expected_lines)
 
 
+@pytest.mark.network
 def test_check_missing_dependency(script):
     # this will also install ipython, a dependency
     script.pip('install', 'ipdb==0.7')
@@ -15,11 +30,14 @@ def test_check_missing_dependency(script):
 
     result = script.pip('check', expect_error=True)
 
-    assert result.stdout == ("ipdb 0.7 requires ipython, "
-                             "which is not installed.\n")
+    expected_lines = (
+        "ipdb 0.7 requires ipython, which is not installed.",
+    )
+    assert matches_expected_lines(result.stdout, expected_lines)
     assert result.returncode == 1
 
 
+@pytest.mark.network
 def test_check_missing_dependency_normalize_case(script):
     # Install some things
     script.pip('install', 'devpi-web==2.2.2')
@@ -31,13 +49,15 @@ def test_check_missing_dependency_normalize_case(script):
 
     result = script.pip('check', expect_error=True)
 
-    assert ('devpi-web 2.2.2 requires pygments, '
-            'which is not installed.') in result.stdout
-    assert ('pyramid 1.5.2 requires zope.deprecation, '
-            'which is not installed.') in result.stdout
+    expected_lines = (
+        "devpi-web 2.2.2 requires pygments, which is not installed.",
+        "pyramid 1.5.2 requires zope.deprecation, which is not installed.",
+    )
+    assert matches_expected_lines(result.stdout, expected_lines)
     assert result.returncode == 1
 
 
+@pytest.mark.network
 def test_check_broken_dependency(script):
     # this will also install a compatible version of jinja2
     script.pip('install', 'flask==0.10.1')
@@ -47,6 +67,31 @@ def test_check_broken_dependency(script):
 
     result = script.pip('check', expect_error=True)
 
-    assert result.stdout == ("Flask 0.10.1 has requirement Jinja2>=2.4, "
-                             "but you have Jinja2 2.3.\n")
+    expected_lines = (
+        "Flask 0.10.1 has requirement Jinja2>=2.4, but you have Jinja2 2.3.",
+    )
+    assert matches_expected_lines(result.stdout, expected_lines)
+    assert result.returncode == 1
+
+
+@pytest.mark.network
+def test_check_broken_dependency_and_missing_dependency(script):
+    # this will also install a compatible version of jinja2
+    script.pip('install', 'flask==0.10.1')
+    script.pip('install', 'pyramid==1.5.2')
+
+    # deliberately remove a dependency
+    script.pip('uninstall', 'zope.deprecation', '--yes')
+
+    # deliberately change dependency to a version that is too old
+    script.pip('install', 'jinja2==2.3')
+
+    result = script.pip('check', expect_error=True)
+
+    expected_lines = (
+        "pyramid 1.5.2 requires zope.deprecation, which is not installed.",
+        "Flask 0.10.1 has requirement Jinja2>=2.4, but you have Jinja2 2.3."
+    )
+
+    assert matches_expected_lines(result.stdout, expected_lines)
     assert result.returncode == 1