Introduce RspecFlaky::ExamplesPruner to prune old flaky examples

Signed-off-by: Rémy Coutable <remy@rymai.me>

lib/rspec_flaky/examples_pruner.rb

+require 'json'
+
+module RspecFlaky
+  class ExamplesPruner
+    # - flaky_examples: contains flaky examples
+    attr_reader :flaky_examples
+
+    def initialize(collection)
+      unless collection.is_a?(RspecFlaky::FlakyExamplesCollection)
+        raise ArgumentError, "`collection` must be a RspecFlaky::FlakyExamplesCollection, #{collection.class} given!"
+      end
+
+      @flaky_examples = collection
+    end
+
+    def prune_examples_older_than(date)
+      updated_hash = flaky_examples.dup
+        .delete_if do |uid, hash|
+          hash[:last_flaky_at] && Time.parse(hash[:last_flaky_at]).to_i < date.to_i
+        end
+
+      RspecFlaky::FlakyExamplesCollection.new(updated_hash)
+    end
+  end
+end

lib/rspec_flaky/flaky_examples_collection.rb

 require 'json'
 
+require_relative 'flaky_example'
+
 module RspecFlaky
   class FlakyExamplesCollection < SimpleDelegator
     def self.from_json(json)

spec/lib/rspec_flaky/examples_pruner_spec.rb

+require 'spec_helper'
+
+describe RspecFlaky::ExamplesPruner, :aggregate_failures do
+  let(:collection_hash) do
+    {
+      a: { example_id: 'spec/foo/bar_spec.rb:2' },
+      b: { example_id: 'spec/foo/baz_spec.rb:3', first_flaky_at: Time.utc(2000, 1, 1).to_s, last_flaky_at: Time.utc(2000, 2, 1).to_s }
+    }
+  end
+
+  describe '#initialize' do
+    it 'accepts a collection' do
+      expect { described_class.new(RspecFlaky::FlakyExamplesCollection.new(collection_hash)) }.not_to raise_error
+    end
+
+    it 'does not accept anything else' do
+      expect { described_class.new([1, 2, 3]) }.to raise_error(ArgumentError, "`collection` must be a RspecFlaky::FlakyExamplesCollection, Array given!")
+    end
+  end
+
+  describe '#prune_examples_older_than' do
+    it 'returns a new collection without the examples older than 3 months' do
+      collection = RspecFlaky::FlakyExamplesCollection.new(collection_hash)
+
+      new_report = collection.to_report.dup.tap { |r| r.delete(:b) }
+      new_collection = described_class.new(collection).prune_examples_older_than(3.months.ago)
+
+      expect(new_collection).to be_a(RspecFlaky::FlakyExamplesCollection)
+      expect(new_collection.to_report).to eq(new_report)
+      expect(collection).to have_key(:b)
+    end
+  end
+end