Allow assertions in mock_app request context

I changed the ".should." style to use "fail" when we
converted to test/unit style but I'd rather use asserts
here.

test/filter_test.rb

@@ -6,11 +6,11 @@ describe "Filters" do
     mock_app do
       get('/') { 'Hello World' }
       before {
-        fail 'count != 0' if count != 0
+        assert_equal 0, count
         count = 1
       }
       before {
-        fail 'count != 1' if count != 1
+        assert_equal 1, count
         count = 2
       }
     end

test/helper.rb

@@ -18,3 +18,8 @@ module Sinatra::Test
     @app = Sinatra.new(base, &block)
   end
 end
+
+class Sinatra::Base
+  # Allow assertions in request context
+  include Test::Unit::Assertions
+end

test/helpers_test.rb

@@ -142,7 +142,7 @@ describe 'Sinatra::Helpers' do
     it 'creates a new session when none provided' do
       mock_app {
         get '/' do
-          fail "session != {}" unless session.empty?
+          assert session.empty?
           session[:foo] = 'bar'
           'Hi'
         end

test/mapped_error_test.rb

@@ -34,8 +34,8 @@ describe 'Exception Mappings' do
     mock_app {
       set :raise_errors, false
       error(FooError) {
-        fail "!env.include?('sinatra.error')" if !env.include?('sinatra.error')
-        fail unless env['sinatra.error'].kind_of?(FooError)
+        assert env.include?('sinatra.error')
+        assert env['sinatra.error'].kind_of?(FooError)
         'looks good'
       }
       get '/' do

test/routing_test.rb

@@ -27,8 +27,8 @@ describe "Routing" do
   it "exposes params with indifferent hash" do
     mock_app {
       get '/:foo' do
-        fail unless params['foo'] == 'bar'
-        fail unless params[:foo] == 'bar'
+        assert_equal 'bar', params['foo']
+        assert_equal 'bar', params[:foo]
         'well, alright'
       end
     }
@@ -39,8 +39,8 @@ describe "Routing" do
   it "merges named params and query string params in params" do
     mock_app {
       get '/:foo' do
-        fail unless params['foo'] == 'bar'
-        fail unless params['baz'] == 'biz'
+        assert_equal 'bar', params['foo']
+        assert_equal 'biz', params['baz']
       end
     }
     get '/bar?baz=biz'
@@ -80,7 +80,7 @@ describe "Routing" do
   it "supports single splat params like /*" do
     mock_app {
       get '/*' do
-        fail unless params['splat'].kind_of?(Array)
+        assert params['splat'].kind_of?(Array)
         params['splat'].join "\n"
       end
     }
@@ -95,7 +95,7 @@ describe "Routing" do
   it "supports mixing multiple splat params like /*/foo/*/*" do
     mock_app {
       get '/*/foo/*/*' do
-        fail unless params['splat'].kind_of?(Array)
+        assert params['splat'].kind_of?(Array)
         params['splat'].join "\n"
       end
     }
@@ -110,8 +110,8 @@ describe "Routing" do
   it "supports mixing named and splat params like /:foo/*" do
     mock_app {
       get '/:foo/*' do
-        fail unless params['foo'] == 'foo'
-        fail unless params['splat'] == ['bar/baz']
+        assert_equal 'foo', params['foo']
+        assert_equal ['bar/baz'], params['splat']
       end
     }
 
@@ -134,8 +134,8 @@ describe "Routing" do
   it "URL decodes named parameters and splats" do
     mock_app {
       get '/:foo/*' do
-        fail unless params['foo'] == 'hello world'
-        fail unless params['splat'] == ['how are you']
+        assert_equal 'hello world', params['foo']
+        assert_equal ['how are you'], params['splat']
         nil
       end
     }
@@ -159,7 +159,7 @@ describe "Routing" do
   it 'makes regular expression captures available in params[:captures]' do
     mock_app {
       get(/^\/fo(.*)\/ba(.*)/) do
-        fail unless params[:captures] == ['orooomma', 'f']
+        assert_equal ['orooomma', 'f'], params[:captures]
         'right on'
       end
     }
@@ -190,7 +190,7 @@ describe "Routing" do
       end
 
       get '/*' do
-        fail if params.include?('foo')
+        assert !params.include?('foo')
         'Hello World'
       end
     }