> For the complete documentation index, see [llms.txt](https://validium.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://validium.gitbook.io/docs/components/prover/circuits/circuit-testing.md).

# Circuit Testing

***

This page explains unit tests for circuits. Specifically, it goes through a unit test of [ecrecover](https://github.com/matter-labs/era-zkevm_circuits/blob/main/src/ecrecover/mod.rs#L796). The tests for other circuits are very similar.

Many of the tests for different circuits are nearly identical, for example:

* test\_signature\_for\_address\_verification (ecrecover)
* test\_code\_unpacker\_inner
* test\_demultiplex\_storage\_logs\_inner
* and several others.

If you understand one, you will quickly be able to understand them all.

Let’s focus on ecrecover. Ecrecover is a precompile that, given your signature, can compute your address. If our circuit works correctly, we should be able to recover the proper address, and be able to prove the computation was done correctly.

![ECRecover testing](https://docs.zksync.io/_ipx/q_90/images/zk-stack/circuit-ecrecover.png)

The test begins by defining `geometry`, `max_variables`, and `max_trace_len`. This data will be used to create the constraint system. Next, we define a helper function:

![ECRecover geometry](https://docs.zksync.io/_ipx/q_90/images/zk-stack/circuits-ecrecover-geometry.png)

To help run the test, we have a helper function called `configure` that returns a builder. The builder knows all of the gates and gate placement strategy, which will be useful for setting up the constraint system.

![Code block showing usage of configure](https://docs.zksync.io/_ipx/q_90/images/zk-stack/circuits-configure-builder.png)

The constraint system is almost ready! We still need to add the lookup tables for common boolean functions:

![Code block showing creation of lookup tables](https://docs.zksync.io/_ipx/q_90/images/zk-stack/circuit-lookup.png)

Now the constraint system is ready! We can start the main part of the test!

![Code block showing signature simulation](https://docs.zksync.io/_ipx/q_90/images/zk-stack/circuits-address.png)

Here we have hard coded a secret key with its associated public key, and generate a signature. We will test our circuit on these inputs! Next we “allocate” these inputs as witnesses:

![Code block showing witness allocation](https://docs.zksync.io/_ipx/q_90/images/zk-stack/circuit-allocate.png)

We have to use special integer types because we are working in a finite field.

![Code block showing integer types](https://docs.zksync.io/_ipx/q_90/images/zk-stack/circuit-finite-fields.png)

The constants here are specific to the curve used, and are described in detail by code comments in the ecrecover\_precompile\_inner\_routine.

Finally we can call the ecrecover\_precompile\_inner\_routine:

![Code block showing ecrecover precompile](https://docs.zksync.io/_ipx/q_90/images/zk-stack/circuit-ecrecover-precompile.png)

Lastly, we need to check to make sure that 1) we recovered the correct address, and 2) the constraint system can be satisfied, meaning the proof works.

![Code block comparing recovered address with original](https://docs.zksync.io/_ipx/q_90/images/zk-stack/circuit-compare-addresses.png)