zio.test.laws
The laws package provides functionality for describing laws as values. The
fundamental abstraction is a set of ZLaws[Caps, R]. These laws model the
laws that instances having a capability of type Caps are expected to
satisfy. A capability Caps[_] is an abstraction describing some
functionality that is common across different data types and obeys certain
laws. For example, we can model the capability of two values of a type being
compared for equality as follows:
trait Equal[-A] {
def equal(a1: A, a2: A): Boolean
}
Definitions of equality are expected to obey certain laws:
- Reflexivity -
a1 === a1 - Symmetry -
a1 === a2 ==> a2 === a1 - Transitivity -
(a1 === a2) && (a2 === a3) ==> (a1 === a3)
These laws define what the capabilities mean and ensure that it is safe to abstract across different instances with the same capability.
Using ZIO Test, we can represent these laws as values. To do so, we define
each law using one of the ZLaws constructors. For example:
val transitivityLaw = ZLaws.Laws3[Equal]("transitivityLaw") {
def apply[A: Equal](a1: A, a2: A, a3: A): TestResult =
???
}
We can then combine laws using the + operator:
val reflexivityLaw: = ???
val symmetryLaw: = ???
val equalLaws = reflexivityLaw + symmetryLaw + transitivityLaw
Laws have a run method that takes a generator of values of type A and
checks that those values satisfy the laws. In addition, objects can extend
ZLawful to provide an even more convenient syntax for users to check that
instances satisfy certain laws.
object Equal extends Lawful[Equal]
object Hash extends Lawful[Hash]
object Ord extends Lawful[Ord]
checkAllLaws(Equal + Hash + Ord)(Gen.int)
Note that capabilities compose seamlessly because of contravariance. We can combine laws describing different capabilities to construct a set of laws requiring that instances having all of the capabilities satisfy each of the laws.
Type members
Classlikes
A GenF knows how to construct a generator of F[A] values given a
generator of A values for any A. For example, a GenF of List values
knows how to generate lists with elements given a generator of elements of
that type. You can think of GenF as a "recipe" for building generators for
parameterized types.
A GenF knows how to construct a generator of F[A] values given a
generator of A values for any A. For example, a GenF of List values
knows how to generate lists with elements given a generator of elements of
that type. You can think of GenF as a "recipe" for building generators for
parameterized types.
- Companion:
- object
A GenF knows how to construct a generator of F[A,B] values given a
generator of A and generator of B values. For example, a GenF2 of
Function1 values knows how to generate functions A => B with elements given
a generator of elements of that type B.
A GenF knows how to construct a generator of F[A,B] values given a
generator of A and generator of B values. For example, a GenF2 of
Function1 values knows how to generate functions A => B with elements given
a generator of elements of that type B.
- Companion:
- object
ZLawful[Caps, R] describes a capability that is expected to satisfy a set
of laws. Lawful instances can be combined using + to describe a set of
capabilities and all of the laws that those capabilities are expected to
satisfy.
ZLawful[Caps, R] describes a capability that is expected to satisfy a set
of laws. Lawful instances can be combined using + to describe a set of
capabilities and all of the laws that those capabilities are expected to
satisfy.
trait Equal[-A] {
def equal(a1: A, a2: A): Boolean
}
object Equal extends Lawful[Equal] {
val laws = ???
}
ZLawfulF[CapsF, Caps, R] describes a set of laws that a parameterized type
F[A] with capabilities CapsF is expected to satisfy with respect to all
types A that have capabilities Caps. Lawful instances can be combined
using + to describe a set of capabilities and all of the laws that those
capabilities are expected to satisfy.
ZLawfulF[CapsF, Caps, R] describes a set of laws that a parameterized type
F[A] with capabilities CapsF is expected to satisfy with respect to all
types A that have capabilities Caps. Lawful instances can be combined
using + to describe a set of capabilities and all of the laws that those
capabilities are expected to satisfy.
ZLaws[Caps, R] represents a set of laws that values with capabilities
Caps are expected to satisfy. Laws can be run by providing a generator of
values of a type A with the required capabilities to return a test result.
Laws can be combined using + to produce a set of laws that require both
sets of laws to be satisfied.
ZLaws[Caps, R] represents a set of laws that values with capabilities
Caps are expected to satisfy. Laws can be run by providing a generator of
values of a type A with the required capabilities to return a test result.
Laws can be combined using + to produce a set of laws that require both
sets of laws to be satisfied.
- Companion:
- object
ZLaws[CapsF, Caps, R] describes a set of laws that a parameterized type
F[A] with capabilities CapsF is expected to satisfy with respect to all
types A that have capabilities Caps. Laws can be run by providing a
GenF that is capable of generating F[A] values given a generator of A
values and a generator of values of some type A. Laws can be combined using
+ to produce a set of laws that require both sets of laws to be satisfied.
ZLaws[CapsF, Caps, R] describes a set of laws that a parameterized type
F[A] with capabilities CapsF is expected to satisfy with respect to all
types A that have capabilities Caps. Laws can be run by providing a
GenF that is capable of generating F[A] values given a generator of A
values and a generator of values of some type A. Laws can be combined using
+ to produce a set of laws that require both sets of laws to be satisfied.
Value members
Concrete methods
Checks that all values generated by a the specified generator satisfy the expected behavior of the lawful instance.
Checks that all values generated by a the specified generator satisfy the expected behavior of the lawful instance.
Checks that all values generated by a the specified generator satisfy the expected behavior of the lawful instance.
Checks that all values generated by a the specified generator satisfy the expected behavior of the lawful instance.
Checks that all values generated by a the specified generator satisfy the expected behavior of the lawful instance.
Checks that all values generated by a the specified generator satisfy the expected behavior of the lawful instance.
Checks that all values generated by a the specified generator satisfy the expected behavior of the lawful instance.
Checks that all values generated by a the specified generator satisfy the expected behavior of the lawful instance.