Show location of difference when comparing two strings

[wilka]

When using string1.Should().Be(string2), if the strings differ it can be awkward to work out where the difference is for large string. E.g. if you're checking that building some json/xml/whatever-long-text works correctly.

Click for example test output for xml text

Expected xmlString1 to be 
"<CATALOG>
	<CD>
		<TITLE>Empire Burlesque</TITLE>
		<ARTIST>Bob Dylan</ARTIST>
		<COUNTRY>USA</COUNTRY>
		<COMPANY>Columbia</COMPANY>
		<PRICE>10.90</PRICE>
		<YEAR>1985</YEAR>
	</CD>
	<CD>
		<TITLE>Hide your heart</TITLE>
		<ARTIST>Bonnie Tyler</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>CBS Records</COMPANY>
		<PRICE>9.90</PRICE>
		<YEAR>1988</YEAR>
	</CD>
	<CD>
		<TITLE>Greatest Hits</TITLE>
		<ARTIST>Dolly Parton</ARTIST>
		<COUNTRY>USA</COUNTRY>
		<COMPANY>RCA</COMPANY>
		<PRICE>19.90</PRICE>
		<YEAR>1982</YEAR>
	</CD>
	<CD>
		<TITLE>Still got the blues</TITLE>
		<ARTIST>Gary Moore</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>Virgin records</COMPANY>
		<PRICE>10.20</PRICE>
		<YEAR>1990</YEAR>
	</CD>
</CATALOG>" with a length of 756, but 
"<CATALOG>
	<CD>
		<TITLE>Empire Burlesque</TITLE>
		<ARTIST>Bob Dylan</ARTIST>
		<COUNTRY>USA</COUNTRY>
		<COMPANY>Columbia</COMPANY>
		<PRICE>10.90</PRICE>
		<YEAR>1985</YEAR>
	</CD>
	<CD>
		<TITLE>Hide your heart</TITLE>
		<ARTIST>Bonnie Tyler</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>CBS Records</COMPANY>
		<PRICE>9.90</PRICE>
		<YEAR>1988</YEAR>
	</CD>
	<CD>
		<TITLE>Greatest Hits</TITLE>
		<ARTIST>Dolly Parton</ARTIST>
		<COUNTRY>USA</COUNTRY>
		<COMPANY>RCA</COMPANY>
		<PRICE>9.90</PRICE>
		<YEAR>1982</YEAR>
	</CD>
	<CD>
		<TITLE>Still got the blues</TITLE>
		<ARTIST>Gary Moore</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>Virgin records</COMPANY>
		<PRICE>10.20</PRICE>
		<YEAR>1990</YEAR>
	</CD>
</CATALOG>" has a length of 755.

At the moment, I'm copy & pasting from the test output into a diff tool so I can find where the difference is.

It would be great if the assert message also included a hint to where to the first difference.

Some ideas that I'd find handy (any of these could go after or before the current message showing the full actual vs expected text)

• For multi-line strings, include the line number of the first difference
• Include a snippet of the string, that shows a few characters before & after the index of the first difference (say 14 characters before the difference, and 6 characters after)
• A unified diff style display of the two strings (like git would show)

The specific details of how to show what the differences are (or at least the first difference) aren't very important, anything that helps speed up tracking down the differences would be 👍

[adamfk]

Did the unified diff idea get implemented? I looked in the related PR and documentation, but didn't see anything.

[dennisdoomen]

No, but we are experimenting with it as we speak. See #2050

[adamfk]

Thanks! I'll keep an eye on it.

[ArmandRedgate]

This issue has been marked as closed 2 years ago, but I notice that the implementation that is being used now seems to be

Include a snippet of the string

Except for me it seems to give only 3 or 4 characters, and those can be nearly impossible to find in a 4000 line yaml file which may have repeating patterns.

Is there still not better option that gives more context? Whether that be:

• Showing a whole line and an arrow
• Having a proper diff view like with git

[dennisdoomen]

In #2307, we improved the comparison a lot. This will be released as part of version 8 (ETA January).