Hegel (hegel_elixir v0.1.1)

View Source

Property-based testing for Elixir, powered by Hegel's Hypothesis-derived engine.

A property receives a Hegel.TestCase and draws values from contextual generators. Hegel runs the property against examples chosen by libhegel, then shrinks each failure.

alias Hegel.Generators, as: Gen

Hegel.check(fn tc ->
  values = Hegel.draw(tc, Gen.list_of(Gen.integer()))
  assert Enum.reverse(Enum.reverse(values)) == values
end)

For ExUnit's property and check all syntax, use Hegel.ExUnit.

Summary

Types

run_result()

Functions

assume(condition)

Rejects the current example using the contextual test case.

assume(test_case, condition)

Rejects the current example when condition is false.

assume(test_case, condition, reason)
check(property, options \\ [])

Runs a property, returning :ok or raising its minimized failure.

draw(generator)

Draws a value using the current property test case.

draw(test_case, generator, metadata \\ %{})

Draws a value from a generator in the current property.

fail(message \\ "property failed")

Marks the current example as a property failure.

note(message)
note(test_case, message)

Attaches diagnostic information to the minimized counterexample.

run(property, options \\ [])

Runs a property and returns a structured result without raising for a discovered counterexample.

sample(generator, options \\ [])

Draws one value outside a property test.

target(value, label)
target(test_case, value, label)

Guides generation toward larger observed values under label.

version()

Returns the exact libhegel engine version compiled into the NIF.

Types

run_result()

@type run_result() :: {:ok, Hegel.Result.t()} | {:error, Hegel.Result.t()}

Functions

assume(condition)

Rejects the current example using the contextual test case.

assume(test_case, condition)

Rejects the current example when condition is false.

assume(test_case, condition, reason)

@spec assume(Hegel.TestCase.t(), term(), term()) :: :ok | no_return()

check(property, options \\ [])

@spec check((Hegel.TestCase.t() -> term()), keyword() | map() | Hegel.Settings.t()) ::
  :ok

Runs a property, returning :ok or raising its minimized failure.

After replaying the minimized blob, Hegel restores the exception kind, reason, and stacktrace. ExUnit can then render its assertion diff.

draw(generator)

@spec draw(Hegel.Generator.t(value)) :: value when value: term()

Draws a value using the current property test case.

draw(test_case, generator, metadata \\ %{})

@spec draw(Hegel.TestCase.t(), Hegel.Generator.t(value), map() | keyword()) :: value
when value: term()

Draws a value from a generator in the current property.

fail(message \\ "property failed")

Marks the current example as a property failure.

note(message)

note(test_case, message)

Attaches diagnostic information to the minimized counterexample.

run(property, options \\ [])

@spec run((Hegel.TestCase.t() -> term()), keyword() | map() | Hegel.Settings.t()) ::
  run_result()

Runs a property and returns a structured result without raising for a discovered counterexample.

Invalid generator configuration and native errors raise before libhegel can treat them as counterexamples. Use check/2 when ExUnit should receive the minimized assertion.

sample(generator, options \\ [])

@spec sample(
  Hegel.Generator.t(value),
  keyword()
) :: value
when value: term()

Draws one value outside a property test.

Sampling uses libhegel's single-test-case mode and performs no shrinking. It is intended for exploration; real tests should use check/2.

target(value, label)

target(test_case, value, label)

Guides generation toward larger observed values under label.

version()

@spec version() :: String.t()

Returns the exact libhegel engine version compiled into the NIF.