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.
Attributes
Members list
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.
Attributes
- Companion
- object
- Supertypes
-
class Objecttrait Matchableclass Any
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
.
Attributes
- Companion
- object
- Supertypes
-
class Objecttrait Matchableclass Any
Attributes
Attributes
- Supertypes
-
class Objecttrait Matchableclass Any
- Self type
-
LawfulF2.type
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 = ???
}
Attributes
- Supertypes
-
class Objecttrait Matchableclass Any
- Self type
-
Attributes
- Supertypes
-
class Objecttrait Matchableclass Any
- Self type
-
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.
Attributes
- Supertypes
-
class Objecttrait Matchableclass Any
- Self type
-
ZLawfulF.type
Attributes
- Supertypes
-
class Objecttrait Matchableclass Any
- Self type
-
ZLawfulF2.type
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.
Attributes
- Companion
- object
- Supertypes
-
class Objecttrait Matchableclass Any
- Known subtypes
- Self type
-
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.
Attributes
- Supertypes
-
class Objecttrait Matchableclass Any
- Self type
-
ZLawsF.type
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.
Attributes
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.
Attributes
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.
Attributes
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.