Debugging Elixir Applications

Debugging Elixir Applications

Debugging is an essential aspect of software development. It allows developers to identify and fix issues in their applications. In this article, we will explore various techniques and tools for debugging Elixir applications.

Logging

Logging is a fundamental debugging technique that provides valuable information about the execution flow of an application. Elixir provides a built-in `Logger` module that allows developers to log messages at different levels of severity. Here is an example of how to use the `Logger` module:

``` Logger.debug("This is a debug message") Logger.info("This is an info message") Logger.warn("This is a warning message") Logger.error("This is an error message") ```

Pry

Pry is a powerful interactive debugger for Elixir that allows developers to pause the execution of their code and inspect variables, functions, and the call stack. To use Pry, you need to add the `pry` package to your project dependencies and use the `require` macro to import the `Pry` module.

```elixir defp deps do

 [
   {:pry, "~> 1.4", only: [:dev, :test]}
 ]

end ```

```elixir require Pry Pry.pry() ```

Debugger

The `:debugger` module in Elixir provides a graphical interface for debugging code. To use the debugger, you need to start it with the `:debugger.start()` function, set breakpoints using the `:debugger.break` function, and then execute your code.

```elixir

debugger.start()

debugger.break({MyModule, :my_function, 1})

MyModule.my_function(arg1, arg2) ```

ExUnit.assert_debug and assert_receive

The `ExUnit.assert_debug` function allows you to assert that a debug message has been logged during the execution of your test. This is useful when you want to ensure that specific debug messages are being logged under certain conditions.

```elixir ExUnit.assert_debug(fn ->

 # Code that should trigger a debug log message

end, "Expected debug message")

ExUnit.assert_receive(fn ->

 # Code that should send a message to a process

end, fn (message) ->

 assert message == expected_message

end) ```

Phoenix LiveDashboard

Phoenix LiveDashboard is a real-time performance monitoring tool that provides detailed insights into the behavior of your application. It allows you to track requests, view process information, and debug issues in real-time. To use LiveDashboard, you need to add the `phoenix_live_dashboard` package to your project dependencies and mount it in your Phoenix router.

```elixir defp deps do

 [
   {:phoenix_live_dashboard, "~> 0.4", only: :dev}
 ]

end ```

```elixir if Mix.env() == :dev do

 scope "/dashboard" do
   pipe_through :browser
   live_dashboard()
 end

end ```

These are some of the techniques and tools available for debugging Elixir applications. By using a combination of logging, interactive debuggers, and specialized testing assertions, developers can efficiently identify and solve issues in their code.