# Right-B[I]CEP: Checking Inverse Relationships

Learn about writing the unit tests with the inverse relationship technique.

## Logical inverse relationships

Sometimes, we’ll be able to check behavior by applying its logical inverse. For mathematical computations, this is often the case. We can:

- Verify division with multiplication
- Verify addition with subtraction

## Implementation of the square-root function

Let’s take a look at the **square-root function** using Newton’s algorithm.

Remember that if we derive the square root of a number and square that result (that is, multiply it by itself), we should get the same number we started with:

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