Better error messages for some of ActiveSupport tests

[#4635 state:resolved]
Signed-off-by: NJosé Valim <jose.valim@gmail.com>

activesupport/test/buffered_logger_test.rb

@@ -69,11 +69,11 @@ def test_should_not_mutate_message
 
       4.times do
         @logger.info 'wait for it..'
-        assert @output.string.empty?, @output.string
+        assert @output.string.empty?, "@output.string should be empty but it is #{@output.string}"
       end
 
       @logger.flush
-      assert !@output.string.empty?, @logger.send(:buffer).size.to_s
+      assert !@output.string.empty?, "@logger.send(:buffer).size.to_s should not be empty but it is empty"
     end
 
     define_method "test_disabling_auto_flush_with_#{disable.inspect}_should_flush_at_max_buffer_size_as_failsafe" do
@@ -82,11 +82,11 @@ def test_should_not_mutate_message
 
       (Logger::MAX_BUFFER_SIZE - 1).times do
         @logger.info 'wait for it..'
-        assert @output.string.empty?, @output.string
+        assert @output.string.empty?, "@output.string should be empty but is #{@output.string}"
       end
 
       @logger.info 'there it is.'
-      assert !@output.string.empty?, @logger.send(:buffer).size.to_s
+      assert !@output.string.empty?, "@logger.send(:buffer).size.to_s should not be empty but it is empty"
     end
   end
 
@@ -102,11 +102,11 @@ def test_should_auto_flush_every_n_messages
 
     4.times do
       @logger.info 'wait for it..'
-      assert @output.string.empty?, @output.string
+      assert @output.string.empty?, "@output.string should be empty but it is #{@output.string}"
     end
 
     @logger.info 'there it is.'
-    assert !@output.string.empty?, @output.string
+    assert !@output.string.empty?, "@output.string should not be empty but it is empty"
   end
 
   def test_should_create_the_log_directory_if_it_doesnt_exist