build: require NUnit 2.5

Previous commit [1] stated something which is not always true
actually: although mono installs a mono-nunit.pc that contains
the mono version (as opposed to NUnit version), some distros
(like Debian/Ubuntu) have made that pc file be a symlink from
/usr/lib/pkg-config/mono-nunit.pc to /usr/lib/pkg-config/nunit-pc.

So the best thing is avoid this mess and only depend on NUnit,
which BTW brings some nice API since version 2.5 (mono embeds
version 2.4.8 [2]):

  Assert.That(actual, Is.EqualTo(expected));

This API is more readable (maps better to English language) and has
the added benefit of providing a way to never confuse again the
parameter *actual* with *expected* that was so easy to switch by
mistake on the older Assert.AreEqual(x,y) syntax.

Some lines are added to the HACKING file about this as well, and
the last test I wrote is converted to this syntax, as the first
real sample to have in the codebase.

[1] https://git.gnome.org/browse/banshee/commit/?id=3891ed1e5aaa7d06497525ab5bfc44110939a369
[2] https://github.com/mono/mono/blob/master/mcs/nunit24/CommonAssemblyInfo.cs

HACKING

@@ -93,6 +93,11 @@ guidelines. If code is in violation, you will be asked to reformat it.
   12. Please write `private` accessors even if the language defaults
     to it in the context you're in.
 
+  13. For tests, use the Assert.That(actual, Is.EqualTo(expected)); syntax,
+      which is more readable, and prevents you from misplacing the expected
+      parameter in the place of the actual parameter (a mistake that is very
+      usual when using the older Assert.AreEqual(,) syntax).
+
 
 .NET API Naming Guidelines
 ==========================

build/m4/shamrock/nunit.m4

@@ -1,7 +1,6 @@
 AC_DEFUN([SHAMROCK_CHECK_NUNIT],
 [
 	NUNIT_REQUIRED=2.4.7
-	MONO_NUNIT_REQUIRED=2.4
 
 	AC_ARG_ENABLE(tests, AC_HELP_STRING([--enable-tests], [Enable NUnit tests]),
 		enable_tests=$enableval, enable_tests="no")
@@ -17,15 +16,7 @@ AC_DEFUN([SHAMROCK_CHECK_NUNIT],
 		AM_CONDITIONAL(ENABLE_TESTS, test "x$do_tests" = "xyes")
 
 		if test "x$do_tests" = "xno"; then
-			PKG_CHECK_MODULES(NUNIT, mono-nunit >= $MONO_NUNIT_REQUIRED,
-				do_tests="yes", do_tests="no")
-
-			AC_SUBST(NUNIT_LIBS)
-			AM_CONDITIONAL(ENABLE_TESTS, test "x$do_tests" = "xyes")
-
-			if test "x$do_tests" = "xno"; then
-				AC_MSG_WARN([Could not find nunit: tests will not be available])
-			fi
+			AC_MSG_WARN([Could not find nunit: tests will not be available])
 		fi
 	fi
 ])

src/Libraries/Lastfm/Lastfm/Tests/LastfmRequestTests.cs

@@ -129,15 +129,15 @@ private void UrisAreEquivalent (string expected, string actual)
             string expected_without_querystring = expected.Substring (0, expected.IndexOf ("?"));
             string actual_without_querystring = actual.Substring (0, actual.IndexOf ("?"));
 
-            Assert.AreEqual (expected_without_querystring, actual_without_querystring);
+            Assert.That (actual_without_querystring, Is.EqualTo (expected_without_querystring));
 
             var expected_parameters = expected.Substring (expected.IndexOf ("?")).Split (new [] {'&'});
             var actual_parameters = new List<string> (actual.Substring (actual.IndexOf ("?")).Split (new [] {'&'}));
 
-            Assert.AreEqual (expected_parameters.Length, actual_parameters.Count);
+            Assert.That (actual_parameters.Count, Is.EqualTo (expected_parameters.Length));
             foreach (var expected_param in expected_parameters) {
-                Assert.IsTrue (actual_parameters.Contains (expected_param),
-                               String.Format ("URI {0} is missing parameter '{1}'", actual, expected_param));
+                Assert.That (actual_parameters.Contains (expected_param),
+                             String.Format ("URI {0} is missing parameter '{1}'", actual, expected_param));
             }
         }