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Language-agnostic mutation testing library for Elixir, Erlang, and other BEAM languages. Evaluates test suite quality by introducing deliberate bugs into code and verifying that tests catch them. Intelligent file filtering, 18 mutation strategies, sound equivalent-mutant handling, and more.

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muex lib muex mutator negate_conditionals.ex
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lib/muex/mutator/negate_conditionals.ex 

defmodule Muex.Mutator.NegateConditionals do

  @moduledoc """

  Mutator that replaces a relational operator with its logical complement.



  - `<`  -> `>=`

  - `>`  -> `<=`

  - `<=` -> `>`

  - `>=` -> `<`



  This is PITest's "Negate Conditionals" semantics: each mutation flips the

  truth value of the condition for every input. It deliberately leaves the

  equality operators (`==`, `!=`, `===`, `!==`) to `Muex.Mutator.Comparison`

  and the directional/boundary shifts (e.g. `<` -> `>`) to that mutator too,

  so the two mutators compose without producing duplicate mutants.

  """



  @behaviour Muex.Mutator



  alias Muex.Mutator.Builders



  @complements %{<: :>=, >: :<=, <=: :>, >=: :<}



  @impl true

  def name, do: "NegateConditionals"



  @impl true

  def description, do: "Replaces a relational operator with its logical complement"



  @impl true

  def supported_languages, do: [Muex.Language.Elixir, Muex.Language.Erlang]



  @impl true

  def mutate(ast, context), do: Builders.operator_swap(ast, context, __MODULE__, @complements)

end