### Setup Development Dependencies

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/README.md

Run this command after cloning the repository to install necessary dependencies for development.

```bash
bin/setup
```

--------------------------------

### Install Crystalball via Bundler

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/README.md

After adding the gem to your Gemfile, run this command to install it.

```bash
bundle install
```

--------------------------------

### Start Interactive Console

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/README.md

Use this command to launch an interactive Ruby console for experimenting with the gem.

```bash
bin/console
```

--------------------------------

### Install Gem Locally

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/README.md

Run this command to install the Crystalball gem onto your local machine.

```bash
bundle exec rake install
```

--------------------------------

### Install Crystalball via gem install

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/README.md

Alternatively, you can install the Crystalball gem directly using the gem install command.

```bash
gem install crystalball
```

--------------------------------

### Start Crystalball MapGenerator

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/docs/index.md

Start the MapGenerator in your `spec_helper` before loading any application files. This configuration registers the CoverageStrategy for profiling.

```ruby
if ENV['CRYSTALBALL'] == 'true'
  Crystalball::MapGenerator.start! do |config|
    config.register Crystalball::MapGenerator::CoverageStrategy.new
  end
end
```

--------------------------------

### Register DescribedClassStrategy

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/docs/map_generators.md

The `DescribedClassStrategy` maps examples to the definition paths of their `described_class` and ancestors. It can also accept a custom execution detector.

```ruby
Crystalball::MapGenerator.start! do |config|
  #...
  config.register Crystalball::MapGenerator::DescribedClassStrategy.new
end
```

```ruby
Crystalball::MapGenerator.start! do |config|
  #...
  config.register Crystalball::MapGenerator::DescribedClassStrategy.new(my_detector)
end
```

--------------------------------

### Register ActionViewStrategy

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/docs/map_generators.md

Integrate Rails-specific strategies by requiring `crystalball/rails`. The `ActionViewStrategy` patches `ActionView::Template#compile!` to map examples to affected views.

```ruby
Crystalball::MapGenerator.start! do |config|
  #...
  config.register Crystalball::MapGenerator::ActionViewStrategy.new
end 
```

--------------------------------

### AssociatedSpecs Strategy Configuration

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/docs/predictors.md

Configure the AssociatedSpecs strategy to define rules for detecting which specs should be included in predictions based on file changes. This strategy does not depend on a previously generated example group map.

```ruby
predictor.use Crystalball::Predictor::AssociatedSpecs.new(
  from: %r{models/(.*).rb},
  to: "./spec/models/%s_spec.rb"
  )
```

--------------------------------

### Run Tests in Development

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/README.md

Execute this command to run the test suite during development.

```bash
rake spec
```

--------------------------------

### Register CoverageStrategy

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/docs/map_generators.md

Use `CoverageStrategy` to detect files covered by a spec, indicating potential breakage if changed. Pass a custom detector object that responds to `#detect`.

```ruby
Crystalball::MapGenerator.start! do |config|
  #...
  config.register Crystalball::MapGenerator::CoverageStrategy.new(my_detector)
end
```

--------------------------------

### Register OneshotCoverageStrategy

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/docs/map_generators.md

Utilize `OneshotCoverageStrategy` for more performant coverage tracking. This strategy is not compatible with existing coverage processes and requires starting/clearing coverage between tests. It accepts `exclude_prefixes` to filter paths.

```ruby
Crystalball::MapGenerator.start! do |config|
  #...
  config.register Crystalball::MapGenerator::OneshotCoverageStrategy.new(exclude_prefixes: %w[vendor/ruby])
end
```

--------------------------------

### Customize Map Filename

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/docs/map_generators.md

Customize the resulting map filename using the `map_storage_path` configuration. This allows for dynamic naming based on environment variables.

```ruby
Crystalball::MapGenerator.start! do |config|
  #...
  config.map_storage_path = "execution_map_#{ENV['TEST_ENV_NUMBER'].to_i}.yml"
end
```

--------------------------------

### ModifiedSchema Strategy Configuration

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/docs/predictors.md

Configure the ModifiedSchema strategy for Rails applications to predict specs affected by database schema changes. Requires a path to a tables map file generated by TablesMapGenerator.

```ruby
predictor.use Crystalball::Rails::Predictor::ModifiedSchema.new(
  tables_map_path: './tables_map.yml'
  )
```

--------------------------------

### Disable Compact Map Output

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/docs/map_generators.md

Configure the `MapGenerator` to produce a plain, readable map instead of the default compact format by setting `config.compact_map = false`.

```ruby
Crystalball::MapGenerator.start! do |config|
  #...
  config.compact_map = false
end
```

--------------------------------

### Add Crystalball to Gemfile

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/README.md

Add this line to your application's Gemfile to include Crystalball in your test dependencies.

```ruby
group :test do
  gem 'gitlab-crystalball'
end
```

--------------------------------

### Custom Prediction Builder with Strategies

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/docs/predictors.md

Define a custom prediction builder by inheriting from Crystalball::RSpec::PredictionBuilder and overloading the predictor method to include additional strategies like ModifiedSupportSpecs.

```ruby
class MyPredictionBuilder < Crystalball::RSpec::PredictionBuilder
    def predictor
      super do |p|
        p.use Crystalball::Predictor::ModifiedSpecs.new
        p.use Crystalball::Predictor::ModifiedExecutionPaths.new
        p.use Crystalball::Predictor::ModifiedSupportSpecs.new
      end
    end
end
```

--------------------------------

### Customize TablesMapGenerator Filename

Source: https://gitlab.com/gitlab-org/ruby/gems/crystalball/-/blob/main/docs/map_generators.md

Customize the output filename for `TablesMapGenerator` using `map_storage_path`. This generator is specific to Rails applications for collecting table-to-model mappings.

```ruby
Crystalball::TablesMapGenerator.start! do |config|
  #...
  config.map_storage_path = 'my_custom_tables_map_name.yml'
end
```

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