C# – Parameterized tests in xUnit

Here’s an example of adding a parameterized unit test in xUnit: To parameterize a unit test, you have to do three things: Add the [Theory] attribute. Add the parameters to the unit test method. In the example above, there are four parameters. Add one [InlineData] for each combo of data you want to test. If … Read more

Algorithm Explained: Sum two big integers the hard way

Problem statement: Sum two big integers that are passed in as strings. Return the sum as a string. In other words, implement the following method: Constraint: Don’t use the built-in BigInteger class (note: this is the name in C# and may have a different name in other languages). Do it the hard way instead. If … Read more

C# – Join strings with a separator, ignoring nulls and empty strings

Normally when you want to join strings using a separator, you’d use string.Join(). However, the problem with string.Join() is it doesn’t ignore nulls or empty strings. Take a look at the following examples: If you want to filter out nulls and empty strings, you can filter the list of strings yourself and pass it into … Read more

Algorithm Explained: Determine if two strings have a substring in common

Problem statement: Given two strings, determine if they have a substring in common. Example: Do “hello world” and “world” have a substring in common? Yes, they both have the substring “world”. Approach What are all the substrings of string? The string “word” is four characters long. It contains 10 substrings between length 1 and 4. … Read more

C# – How to create a custom exception

To create a custom exception, create a subclass of the Exception class, like this: Then throw it just like you would any other exception, like this: It’s a good idea to pass in a custom error message to the base constructor. If this exception is unhandled, or if you are logging the exception, then it’ll … Read more

C# – Use DynamicData attribute to pass functions and objects into parameterized tests

The purpose of parameterized tests is to eliminate duplicated tests. There are two ways to pass parameters into a parameterized test: the DataRow attribute and the DynamicData attribute. With DataRow, the problem is you can only pass in constants and arrays. You can’t pass in reference types. When you try to pass in reference types, … Read more