TestIORuntime final

final class TestIORuntime extends IORuntime

A deterministic IORuntime for testing IO programs.

Unlike RealIORuntime, time does not advance automatically. Instead, the test controls time via advance, tick, tickOne, tickAll, and advanceAndTick. Scheduled tasks are stored in a priority queue ordered by their scheduled execution time.

This allows tests to exercise time-dependent logic (e.g. IO.sleep, timeouts, retry delays) without real wall-clock delays.

Inheritance

Object → IORuntime → TestIORuntime

Constructors

TestIORuntime()

TestIORuntime({int autoCedeN = DefaultAutoCedeN})

Implementation

TestIORuntime({super.autoCedeN});

Properties

autoCedeN final inherited

final int autoCedeN

The number of run loop iterations the interpreter will execute before automatically ceding control back to the event loop.

Lower values improve fairness between fibers at the cost of throughput. Must be greater than 0.

Inherited from IORuntime.

Implementation

final int autoCedeN;

hashCode no setter inherited

int get hashCode

The hash code for this object.

A hash code is a single integer which represents the state of the object that affects operator == comparisons.

All objects have hash codes. The default hash code implemented by Object represents only the identity of the object, the same way as the default operator == implementation only considers objects equal if they are identical (see identityHashCode).

If operator == is overridden to use the object state instead, the hash code must also be changed to represent that state, otherwise the object cannot be used in hash based data structures like the default Set and Map implementations.

Hash codes must be the same for objects that are equal to each other according to operator ==. The hash code of an object should only change if the object changes in a way that affects equality. There are no further requirements for the hash codes. They need not be consistent between executions of the same program and there are no distribution guarantees.

Objects that are not equal are allowed to have the same hash code. It is even technically allowed that all instances have the same hash code, but if clashes happen too often, it may reduce the efficiency of hash-based data structures like HashSet or HashMap.

If a subclass overrides hashCode, it should override the operator == operator as well to maintain consistency.

Inherited from Object.

Implementation

external int get hashCode;

now no setter override

DateTime get now

Returns the current time.

Implementation

@override
DateTime get now => DateTime(1970).copyWith(microsecond: _currentMicros);

runtimeType no setter inherited

Type get runtimeType

A representation of the runtime type of the object.

Inherited from Object.

Implementation

external Type get runtimeType;

Methods

advance()

void advance(Duration amount)

Advances the internal clock by amount without executing any tasks.

Implementation

void advance(Duration amount) {
  if (!amount.isNegative) _currentMicros += amount.inMicroseconds;
}

advanceAndTick()

void advanceAndTick(Duration amount)

Advances the clock by amount and then executes all tasks that are now due.

Implementation

void advanceAndTick(Duration amount) {
  advance(amount);
  tick();
}

nextInterval()

Duration nextInterval()

Returns the duration until the next scheduled task, or Duration.zero if the task queue is empty or the next task is already due.

Implementation

Duration nextInterval() {
  if (_tasks.isEmpty) {
    return Duration.zero;
  } else {
    final diff = _tasks.first.runsAt - Duration(microseconds: _currentMicros);
    return diff.isNegative ? Duration.zero : diff;
  }
}

noSuchMethod() inherited

dynamic noSuchMethod(Invocation invocation)

Invoked when a nonexistent method or property is accessed.

A dynamic member invocation can attempt to call a member which doesn't exist on the receiving object. Example:

dynamic object = 1;
object.add(42); // Statically allowed, run-time error

This invalid code will invoke the noSuchMethod method of the integer 1 with an Invocation representing the .add(42) call and arguments (which then throws).

Classes can override noSuchMethod to provide custom behavior for such invalid dynamic invocations.

A class with a non-default noSuchMethod invocation can also omit implementations for members of its interface. Example:

class MockList<T> implements List<T> {
  noSuchMethod(Invocation invocation) {
    log(invocation);
    super.noSuchMethod(invocation); // Will throw.
  }
}
void main() {
  MockList().add(42);
}

This code has no compile-time warnings or errors even though the MockList class has no concrete implementation of any of the List interface methods. Calls to List methods are forwarded to noSuchMethod, so this code will log an invocation similar to Invocation.method(#add, [42]) and then throw.

If a value is returned from noSuchMethod, it becomes the result of the original invocation. If the value is not of a type that can be returned by the original invocation, a type error occurs at the invocation.

The default behavior is to throw a NoSuchMethodError.

Inherited from Object.

Implementation

@pragma("vm:entry-point")
@pragma("wasm:entry-point")
external dynamic noSuchMethod(Invocation invocation);

schedule() override

void schedule(void Function() task)

Schedules task for asynchronous execution on the event loop.

Implementation

@override
void schedule(Function0<void> task) {
  _addTask(_Task(_currentID++, task, Duration(microseconds: _currentMicros)));
}

scheduleAfter() override

void Function() scheduleAfter(Duration delay, void Function() onWake)

Schedules onWake after delay and returns a cancellation function.

Implementation

@override
Function0<void> scheduleAfter(Duration delay, Function0<void> onWake) {
  final newId = _currentID++;
  final clock = _currentMicros;
  final offset = delay >= Duration.zero ? delay : Duration.zero;
  final runsAt = Duration(microseconds: clock) + offset;

  final task = _Task(newId, onWake, runsAt);
  return _addTask(task);
}

tick()

void tick()

Executes all tasks whose scheduled time has arrived, in order.

Implementation

void tick() {
  while (tickOne()) {}
}

tickAll()

void tickAll()

Repeatedly advances the clock to the next scheduled task and executes it until no tasks remain.

Implementation

void tickAll() {
  tick();

  while (_tasks.isNotEmpty) {
    advance(nextInterval());
    tick();
  }
}

tickOne()

bool tickOne()

Executes the earliest scheduled task if its scheduled time has arrived.

Returns true if a task was executed, false otherwise.

Implementation

bool tickOne() {
  return Option(_tasks.firstOrNull).fold(
    () => false,
    (head) {
      if (head.runsAt <= Duration(microseconds: _currentMicros)) {
        final task = _tasks.removeAt(0);

        try {
          task.task();
          return true;
        } catch (_) {
          return false;
        }
      } else {
        return false;
      }
    },
  );
}

toString() inherited

String toString()

A string representation of this object.

Some classes have a default textual representation, often paired with a static parse function (like int.parse). These classes will provide the textual representation as their string representation.

Other classes have no meaningful textual representation that a program will care about. Such classes will typically override toString to provide useful information when inspecting the object, mainly for debugging or logging.

Inherited from Object.

Implementation

external String toString();

Operators

operator ==() inherited

bool operator ==(Object other)

The equality operator.

The default behavior for all Objects is to return true if and only if this object and other are the same object.

Override this method to specify a different equality relation on a class. The overriding method must still be an equivalence relation. That is, it must be:

• Total: It must return a boolean for all arguments. It should never throw.

• Reflexive: For all objects o, o == o must be true.

• Symmetric: For all objects o1 and o2, o1 == o2 and o2 == o1 must either both be true, or both be false.

• Transitive: For all objects o1, o2, and o3, if o1 == o2 and o2 == o3 are true, then o1 == o3 must be true.

The method should also be consistent over time, so whether two objects are equal should only change if at least one of the objects was modified.

If a subclass overrides the equality operator, it should override the hashCode method as well to maintain consistency.

Inherited from Object.

Implementation

external bool operator ==(Object other);