A GenF
knows how to construct a generator of F[A]
values given a
generator of A
values for any A
.
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,B]
values given a
generator of A
and generator of B
values.
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
.
ZLawful[Caps, R]
describes a capability that is expected to satisfy a set
of laws.
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 = ??? }
ZLaws[Caps, R]
represents a set of laws that values with capabilities
Caps
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.
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
.
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[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
.
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.
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.
The
laws
package provides functionality for describing laws as values. The fundamental abstraction is a set ofZLaws[Caps, R]
. These laws model the laws that instances having a capability of typeCaps
are expected to satisfy. A capabilityCaps[_]
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:Definitions of equality are expected to obey certain laws:
a1 === a1
a1 === a2 ==> a2 === a1
(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:We can then combine laws using the
+
operator:Laws have a
run
method that takes a generator of values of typeA
and checks that those values satisfy the laws. In addition, objects can extendZLawful
to provide an even more convenient syntax for users to check that instances satisfy certain laws.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.