Object containing one apply
factory method for each TableFor<n>
class.
Performs a property check by applying the specified property check function to each row
of the specified TableFor22
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor22
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor21
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor21
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor20
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor20
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor19
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor19
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor18
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor18
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor17
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor17
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor16
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor16
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor15
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor15
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor14
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor14
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor13
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor13
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor12
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor12
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor11
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor11
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor10
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor10
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor9
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor9
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor8
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor8
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor7
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor7
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor6
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor6
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor5
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor5
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor4
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor4
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor3
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor3
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor2
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor2
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor1
and succeeding if at least one element satisfies the property check.
Performs a property check by applying the specified property check function to each row
of the specified TableFor1
and succeeding if at least one element satisfies the property check.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor22
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor22
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor21
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor21
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor20
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor20
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor19
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor19
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor18
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor18
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor17
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor17
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor16
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor16
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor15
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor15
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor14
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor14
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor13
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor13
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor12
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor12
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor11
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor11
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor10
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor10
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor9
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor9
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor8
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor8
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor7
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor7
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor6
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor6
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor5
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor5
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor4
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor4
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor3
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor3
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor2
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor2
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor1
.
Performs a property check by applying the specified property check function to each row
of the specified TableFor1
.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor22
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor22
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor21
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor21
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor20
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor20
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor19
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor19
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor18
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor18
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor17
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor17
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor16
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor16
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor15
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor15
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor14
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor14
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor13
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor13
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor12
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor12
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor11
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor11
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor10
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor10
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor9
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor9
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor8
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor8
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor7
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor7
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor6
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor6
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor5
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor5
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor4
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor4
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor3
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor3
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor2
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor2
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Performs a property check by applying the specified property check function to each row
of the specified TableFor1
and reporting every error.
Performs a property check by applying the specified property check function to each row
of the specified TableFor1
and reporting every error.
The difference between forEvery
and forAll
is that
forEvery
will continue to inspect all elements after first failure, and report all failures,
whereas forAll
will stop on (and only report) the first failure.
the table of data with which to perform the property check
the property check function to apply to each row of data in the table
Evaluates the passed code block if the passed boolean condition is true, else throws DiscardedEvaluationException
.
Evaluates the passed code block if the passed boolean condition is true, else throws DiscardedEvaluationException
.
The whenever
method can be used inside property check functions to discard invocations of the function with
data for which it is known the property would fail. For example, given the following Fraction
class:
class Fraction(n: Int, d: Int) { require(d != 0) require(d != Integer.MIN_VALUE) require(n != Integer.MIN_VALUE) val numer = if (d < 0) -1 * n else n val denom = d.abs override def toString = numer + " / " + denom }
import org.scalatest.prop.TableDrivenPropertyChecks._ val fractions = Table( ("n", "d"), ( 1, 2), ( -1, 2), ( 1, -2), ( -1, -2), ( 3, 1), ( -3, 1), ( -3, 0), ( 3, -1), ( 3, Integer.MIN_VALUE), (Integer.MIN_VALUE, 3), ( -3, -1) )
Imagine you wanted to check a property against this class with data that includes some
value that are rejected by the constructor, such as a denominator of zero, which should
result in an IllegalArgumentException
. You could use whenever
to discard any rows in the fraction
that represent illegal arguments, like this:
import org.scalatest.matchers.Matchers._ forAll (fractions) { (n: Int, d: Int) => whenever (d != 0 && d != Integer.MIN_VALUE && n != Integer.MIN_VALUE) { val f = new Fraction(n, d) if (n < 0 && d < 0 || n > 0 && d > 0) f.numer should be > 0 else if (n != 0) f.numer should be < 0 else f.numer should === (0) f.denom should be > 0 } }
In this example, rows 6, 8, and 9 have values that would cause a false to be passed
to whenever
. (For example, in row 6, d
is 0, which means d
!=
0
will be false.) For those rows, whenever
will throw DiscardedEvaluationException
,
which will cause the forAll
method to discard that row.
the boolean condition that determines whether whenever
will evaluate the
fun
function (condition
is true) or throws DiscardedEvaluationException
(condition
is false)
the function to evaluate if the specified condition
is true
Trait containing methods that faciliate property checks against tables of data.
This trait contains one
exists
,forAll
, andforEvery
method for eachTableForN
class,TableFor1
throughTableFor22
, which allow properties to be checked against the rows of a table. It also contains awherever
method that can be used to indicate a property need only hold whenever some condition is true.For an example of trait
TableDrivenPropertyChecks
in action, imagine you want to test thisFraction
class:TableDrivenPropertyChecks
allows you to create tables with between 1 and 22 columns and any number of rows. You create a table by passing tuples to one of the factory methods of objectTable
. Each tuple must have the same arity (number of members). The first tuple you pass must all be strings, because it define names for the columns. Subsequent tuples define the data. After the initial tuple that contains string column names, all tuples must have the same type. For example, if the first tuple after the column names contains twoInt
s, all subsequent tuples must contain twoInt
(i.e., have typeTuple2[Int, Int]
).To test the behavior of
Fraction
, you could create a table of numerators and denominators to pass to the constructor of theFraction
class using one of theapply
factory methods declared inTable
, like this:You could then check a property against each row of the table using a
forAll
method, like this:Trait
TableDrivenPropertyChecks
provides 22 overloadedexists
,forAll
, andforEvery
methods that allow you to check properties using the data provided by a table. Eachexists
,forAll
, andforEvery
method takes two parameter lists. The first parameter list is a table. The second parameter list is a function whose argument types and number matches that of the tuples in the table. For example, if the tuples in the table supplied toforAll
each contain anInt
, aString
, and aList[Char]
, then the function supplied toforAll
must take 3 parameters, anInt
, aString
, and aList[Char]
. TheforAll
method will pass each row of data to the function, and generate aTableDrivenPropertyCheckFailedException
if the function completes abruptly for any row of data with any exception that would normally cause a test to fail in ScalaTest other thanDiscardedEvaluationException
. ADiscardedEvaluationException
, which is thrown by thewhenever
method (also defined in this trait) to indicate a condition required by the property function is not met by a row of passed data, will simply causeforAll
to skip that row of data.The full list of table methods are:
exists
- succeeds if the assertion holds true for at least one elementforAll
- succeeds if the assertion holds true for every elementforEvery
- same asforAll
, but lists all failing elements if it fails (whereasforAll
just reports the first failing element) and throwsTestFailedException
with the first failed check as the cause.Testing stateful functions
One way to use a table with one column is to test subsequent return values of a stateful function. Imagine, for example, you had an object named
FiboGen
whosenext
method returned the next fibonacci number, where next means the next number in the series following the number previously returned bynext
. So the first timenext
was called, it would return 0. The next time it was called it would return 1. Then 1. Then 2. Then 3, and so on.FiboGen
would need to maintain state, because it has to remember where it is in the series. In such a situation, you could create aTableFor1
(a table with one column, which you could alternatively think of as one row), in which each row represents the next value you expect.Then in your
forAll
simply call the function and compare it with the expected return value, like this:Testing mutable objects
If you need to test a mutable object, one way you can use tables is to specify state transitions in a table. For example, imagine you wanted to test this mutable
Counter
class:A
Counter
keeps track of how many times itsclick
method is called. The count starts out at zero and increments with eachclick
invocation. You can also set the count to a specific value by callingenter
and passing the value in. And thereset
method returns the count back to zero. You could define the actions that initiate state transitions with case classes, like this:Given these actions, you could define a state-transition table like this:
To use this in a test, simply do a pattern match inside the function you pass to
forAll
. Make a pattern for each action, and have the body perform that action when there's a match. Then check that the actual value equals the expected value:Testing invalid argument combinations
A table-driven property check can also be helpful to ensure that the proper exception is thrown when invalid data is passed to a method or constructor. For example, the
Fraction
constructor shown above should throwIllegalArgumentException
ifInteger.MIN_VALUE
is passed for either the numerator or denominator, or zero is passed for the denominator. This yields the following five combinations of invalid data:n
d
Integer.MIN_VALUE
Integer.MIN_VALUE
Integer.MIN_VALUE
Integer.MIN_VALUE
Integer.MIN_VALUE
You can express these combinations in a table:
Given this table, you could check that all invalid combinations produce
IllegalArgumentException
, like this: