%{
  title: "How We Test LiveView at Scale",
  author: "Carlos Rivera",
  tags: ~w(elixir liveview testing),
  description: "Our testing strategy for 200+ LiveView modules"
}
---
*This is a sample blog post, generated to show what blogex can do.*

With over 200 LiveView modules in our codebase, we needed a testing strategy
that was both fast and reliable. Here's what we landed on.

## The three-layer approach

We test LiveViews at three levels:

1. **Unit tests** for the assign logic — pure functions, no rendering
2. **Component tests** for individual function components using `render_component/2`
3. **Integration tests** for full page flows using `live/2`

The key insight is that most bugs live in the assign logic, not in the
templates. By extracting assigns into pure functions, we can test the
interesting bits without mounting a LiveView at all.

```elixir
defmodule MyAppWeb.DashboardLive do
  use MyAppWeb, :live_view

  # Pure function — easy to test
  def compute_metrics(raw_data, date_range) do
    raw_data
    |> Enum.filter(&in_range?(&1, date_range))
    |> Enum.group_by(& &1.category)
    |> Enum.map(fn {cat, items} ->
      %{category: cat, count: length(items), total: Enum.sum_by(items, & &1.value)}
    end)
  end
end

# In the test file
test "compute_metrics groups and sums correctly" do
  data = [
    %{category: "sales", value: 100, date: ~D[2026-03-01]},
    %{category: "sales", value: 200, date: ~D[2026-03-02]},
    %{category: "support", value: 50, date: ~D[2026-03-01]}
  ]

  result = DashboardLive.compute_metrics(data, {~D[2026-03-01], ~D[2026-03-31]})

  assert [
    %{category: "sales", count: 2, total: 300},
    %{category: "support", count: 1, total: 50}
  ] = Enum.sort_by(result, & &1.category)
end
```

## Speed matters

Our full test suite runs in under 90 seconds on CI. The secret is
`async: true` everywhere and avoiding database writes in unit tests.
We use `Mox` for external service boundaries and `Ecto.Adapters.SQL.Sandbox`
only for integration tests.

## What we'd do differently

If starting over, we'd adopt property-based testing with `StreamData` earlier.
Several production bugs would have been caught by generating edge-case assigns
rather than hand-writing examples.
