Rheo.Clock.Frozen (rheo v1.0.0)

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Controllable clock for tests and demos.

Configure config :rheo, clock: Rheo.Clock.Frozen then call set/1 or advance/1 to simulate lease expiry without sleeping.

Summary

Functions

advance(ms)

Advances the frozen clock by ms milliseconds.

reset()

Clears the frozen value so utc_now/0 uses the wall clock again.

set(dt)

Sets the frozen clock to a specific DateTime.

utc_now()

Returns the frozen clock's current time.

Functions

advance(ms)

@spec advance(non_neg_integer()) :: :ok

Advances the frozen clock by ms milliseconds.

Examples

iex> Rheo.Clock.Frozen.set(~U[2026-01-15 12:00:00.000Z])
:ok
iex> Rheo.Clock.Frozen.advance(1_500)
:ok
iex> Rheo.Clock.Frozen.utc_now()
~U[2026-01-15 12:00:01.500Z]

Arguments

  • ms — non-negative integer milliseconds

Returns

:ok

Errors

Raises FunctionClauseError when ms is negative or not an integer.

reset()

@spec reset() :: :ok

Clears the frozen value so utc_now/0 uses the wall clock again.

Examples

iex> Rheo.Clock.Frozen.set(~U[2026-01-15 12:00:00.000Z])
:ok
iex> Rheo.Clock.Frozen.reset()
:ok
iex> match?(%DateTime{}, Rheo.Clock.Frozen.utc_now())
true

Returns

:ok

set(dt)

@spec set(DateTime.t()) :: :ok

Sets the frozen clock to a specific DateTime.

Examples

iex> Rheo.Clock.Frozen.set(~U[2026-06-01 08:30:00.000Z])
:ok
iex> Rheo.Clock.Frozen.utc_now()
~U[2026-06-01 08:30:00.000Z]

Arguments

  • dt — UTC DateTime.t(); truncated to milliseconds

Returns

:ok

utc_now()

@spec utc_now() :: DateTime.t()

Returns the frozen clock's current time.

When unset, falls back to the real wall clock.

Examples

iex> Rheo.Clock.Frozen.set(~U[2026-01-15 12:00:00.000Z])
:ok
iex> Rheo.Clock.Frozen.utc_now()
~U[2026-01-15 12:00:00.000Z]

Returns

A DateTime.t().