feat: Add arbitrary ints (with shrinking support) (#152)

fuzzer/api/src/commonMain/kotlin/com/github/jcornaz/kwik/fuzzer/api/simplifier/SimplifierFactory.kt

@@ -2,9 +2,11 @@ package com.github.jcornaz.kwik.fuzzer.api.simplifier
 
 import com.github.jcornaz.kwik.fuzzer.api.ExperimentalKwikFuzzer
 
+/**
+ * Returns a simplifier that use the given [simplify] function to find simpler values
+ */
 @ExperimentalKwikFuzzer
-internal fun <T> simplifier(simplify: (T) -> Sequence<T>): Simplifier<T> = object :
-    Simplifier<T> {
+fun <T> simplifier(simplify: (T) -> Sequence<T>): Simplifier<T> = object : Simplifier<T> {
     override fun simplify(value: T): Sequence<T> = simplify(value)
 }
 

fuzzer/stdlib/build.gradle.kts

@@ -0,0 +1,10 @@
+kotlin {
+    sourceSets {
+        commonMain {
+            dependencies {
+                api(project(":fuzzer-api"))
+                implementation(project(":generator-stdlib"))
+            }
+        }
+    }
+}

fuzzer/stdlib/src/commonMain/kotlin/com/github/jcornaz/kwik/fuzzer/stdlib/Fuzzers.kt

@@ -0,0 +1,35 @@
+package com.github.jcornaz.kwik.fuzzer.stdlib
+
+import com.github.jcornaz.kwik.fuzzer.api.Arbitrary
+import com.github.jcornaz.kwik.fuzzer.api.ExperimentalKwikFuzzer
+import com.github.jcornaz.kwik.fuzzer.api.Fuzzer
+import com.github.jcornaz.kwik.fuzzer.api.simplifier.Simplifier
+import com.github.jcornaz.kwik.fuzzer.api.simplifier.filter
+import com.github.jcornaz.kwik.fuzzer.api.toFuzzer
+import com.github.jcornaz.kwik.fuzzer.stdlib.simplifier.int
+import com.github.jcornaz.kwik.generator.api.Generator
+import com.github.jcornaz.kwik.generator.stdlib.ints
+
+/**
+ * Returns a [Fuzzer] generating [Int] inputs that are between the given [min] anx [max] values.
+ *
+ * The generated inputs have high probability to be [Int.MIN_VALUE], [Int.MAX_VALUE], `-1`, `1` or `0`
+ */
+@ExperimentalKwikFuzzer
+fun Arbitrary.int(min: Int = Int.MIN_VALUE, max: Int = Int.MAX_VALUE): Fuzzer<Int> {
+    val range = min..max
+
+    return Generator.ints(min, max)
+        .toFuzzer(Simplifier.int.filter { it in range })
+}
+
+/**
+ * Returns a [Fuzzer] generating [Int] inputs.
+ *
+ * The generated inputs have high probability to be [Int.MIN_VALUE], [Int.MAX_VALUE], `-1`, `1` or `0`
+ */
+@ExperimentalKwikFuzzer
+fun Arbitrary.int(): Fuzzer<Int> = anyInt
+
+@ExperimentalKwikFuzzer
+private val anyInt: Fuzzer<Int> by lazy { Generator.ints().toFuzzer(Simplifier.int) }

fuzzer/stdlib/src/commonMain/kotlin/com/github/jcornaz/kwik/fuzzer/stdlib/simplifier/Primitives.kt

@@ -0,0 +1,33 @@
+package com.github.jcornaz.kwik.fuzzer.stdlib.simplifier
+
+import com.github.jcornaz.kwik.fuzzer.api.ExperimentalKwikFuzzer
+import com.github.jcornaz.kwik.fuzzer.api.simplifier.Simplifier
+import kotlin.math.absoluteValue
+
+/**
+ * Returns a simplifier capable of simplifying [Int].
+ *
+ * zero is the simplest value.
+ * the closest to zero, the simpler.
+ * positive values are also considered simpler than their negative counterpart.
+ */
+@ExperimentalKwikFuzzer
+val Simplifier.Companion.int: Simplifier<Int>
+    get() = IntSimplifier
+
+@ExperimentalKwikFuzzer
+private object IntSimplifier : Simplifier<Int> {
+    override fun simplify(value: Int): Sequence<Int> = when (value) {
+        0 -> emptySequence()
+        1 -> sequenceOf(0)
+        -1 -> sequenceOf(0, 1)
+        else -> sequence {
+            yield(value / 2)
+
+            if (value < 0) yield(value.absoluteValue)
+
+            if (value.absoluteValue > 2)
+                yield(if (value < 0) value + 1 else value - 1)
+        }
+    }
+}

fuzzer/stdlib/src/commonTest/kotlin/com/github/jcornaz/kwik/fuzzer/stdlib/ArbitraryIntTest.kt

@@ -0,0 +1,79 @@
+package com.github.jcornaz.kwik.fuzzer.stdlib
+
+import com.github.jcornaz.kwik.fuzzer.api.Arbitrary
+import com.github.jcornaz.kwik.fuzzer.api.ExperimentalKwikFuzzer
+import com.github.jcornaz.kwik.fuzzer.api.simplifier.Simplifier
+import com.github.jcornaz.kwik.fuzzer.api.simplifier.filter
+import com.github.jcornaz.kwik.fuzzer.stdlib.simplifier.int
+import com.github.jcornaz.kwik.generator.api.Generator
+import com.github.jcornaz.kwik.generator.api.randomSequence
+import com.github.jcornaz.kwik.generator.stdlib.ints
+import kotlin.random.Random
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+@ExperimentalKwikFuzzer
+class ArbitraryIntTest {
+
+    @Test
+    fun usesIntGenerator() {
+        assertEquals(
+            Generator.ints(32, 54).drawSample(),
+            Arbitrary.int(32, 54).generator.drawSample()
+        )
+    }
+
+    @Test
+    fun hasSameDefaultsThanGenerator() {
+        assertEquals(
+            Generator.ints().drawSample(),
+            Arbitrary.int().generator.drawSample()
+        )
+    }
+
+    @Test
+    fun hasSameDefaultMinThanGenerator() {
+        assertEquals(
+            Generator.ints(max = 34).drawSample(),
+            Arbitrary.int(max = 34).generator.drawSample()
+        )
+    }
+
+    @Test
+    fun hasSameDefaultMaxThanGenerator() {
+        assertEquals(
+            Generator.ints(min = 34).drawSample(),
+            Arbitrary.int(min = 34).generator.drawSample()
+        )
+    }
+
+    @Test
+    fun doesNotHaveAnyGuarantee() {
+        assertTrue(Arbitrary.int().guarantees.isEmpty())
+    }
+
+    @Test
+    fun useIntSimplifier() {
+        repeat(1000) {
+            val initialValue = Random.nextInt()
+            assertEquals(
+                Simplifier.int.simplify(initialValue).toList(),
+                Arbitrary.int().simplifier.simplify(initialValue).toList()
+            )
+        }
+    }
+
+    @Test
+    fun simplifierIsFiltered() {
+        Generator.create { it.nextInt(-100, 100) }
+            .randomSequence(0)
+            .take(1000)
+            .forEach { initialValue ->
+                assertEquals(
+                    Simplifier.int.filter { it in 0..100 }.simplify(initialValue).toList(),
+                    Arbitrary.int(0, 100).simplifier.simplify(initialValue).toList()
+                )
+            }
+    }
+}

fuzzer/stdlib/src/commonTest/kotlin/com/github/jcornaz/kwik/fuzzer/stdlib/Utils.kt

@@ -0,0 +1,7 @@
+package com.github.jcornaz.kwik.fuzzer.stdlib
+
+import com.github.jcornaz.kwik.generator.api.Generator
+import com.github.jcornaz.kwik.generator.api.randomSequence
+
+
+fun <T> Generator<T>.drawSample() = randomSequence(0).take(100).toList()

fuzzer/stdlib/src/commonTest/kotlin/com/github/jcornaz/kwik/fuzzer/stdlib/simplifier/IntSimplifierTest.kt

@@ -0,0 +1,110 @@
+package com.github.jcornaz.kwik.fuzzer.stdlib.simplifier
+
+import com.github.jcornaz.kwik.fuzzer.api.ExperimentalKwikFuzzer
+import com.github.jcornaz.kwik.fuzzer.api.simplifier.Simplifier
+import com.github.jcornaz.kwik.fuzzer.api.simplifier.findSimplestFalsification
+import com.github.jcornaz.kwik.generator.api.*
+import kotlin.math.abs
+import kotlin.random.Random
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+@ExperimentalKwikFuzzer
+class IntSimplifierTest {
+    private val anyInt = Generator.create(Random::nextInt)
+    private val anyNegativeInt = Generator.create { it.nextInt(Int.MIN_VALUE, -1) }
+
+    @Test
+    fun zeroIsTheSimplestValue() {
+        assertTrue(Simplifier.int.simplify(0).none())
+    }
+
+    @Test
+    fun zeroIsSimplerThanOne() {
+        assertEquals(0, Simplifier.int.simplify(1).single())
+    }
+
+    @Test
+    fun zeroIsSimplerThanMinusOne() {
+        assertTrue(Simplifier.int.simplify(-1).any { it == 0 })
+    }
+
+    @Test
+    fun positiveIsSimplerThanNegative() {
+        val simplifier = Simplifier.int
+
+        Generator.frequency(
+            1.0 to Generator.of(-2, -1),
+            2.0 to anyNegativeInt
+        )
+            .randomSequence(0)
+            .take(200)
+            .forEach { value ->
+                assertTrue(simplifier.simplify(value).any { it == abs(value) })
+            }
+    }
+
+    @Test
+    fun nonZeroValueHaveSimplerValues() {
+        Generator.frequency(
+            1.0 to Generator.of(-2, -1, 1, 2),
+            2.0 to anyInt.filterNot { it == 0 }
+        )
+            .randomSequence(0)
+            .take(200)
+            .forEach { value ->
+                assertTrue(Simplifier.int.simplify(value).any())
+            }
+    }
+
+    @Test
+    fun simplerValuesAreCloserToZero() {
+        Generator.frequency(
+            1.0 to Generator.of(-2, -1, 1, 2),
+            2.0 to anyInt.filterNot { it == 0 }
+        )
+            .randomSequence(0)
+            .take(200)
+            .forEach { value ->
+                assertTrue(Simplifier.int.simplify(value).all {
+                    (it == abs(value)) || (abs(it) < abs(value))
+                })
+            }
+    }
+
+    @Test
+    fun returnsDistinctSequence() {
+        Generator.frequency(
+            2.0 to Generator.of((-2)..2),
+            1.0 to anyInt
+        )
+            .randomSequence(0)
+            .take(200)
+            .forEach { value ->
+                val set = HashSet<Int>()
+                assertTrue(Simplifier.int.simplify(value).all(set::add))
+            }
+    }
+
+    @Test
+    fun allowToFindSimplerFalsifyingValue() {
+        val passRange = (-42)..1337
+
+        Generator.create { it.nextInt(Int.MIN_VALUE, passRange.first - 1) }
+            .plus(Generator.create { it.nextInt(passRange.last + 1, Int.MAX_VALUE) })
+            .randomSequence(0)
+            .take(200)
+            .forEach { initialValue ->
+                val simplestValue =
+                    Simplifier.int
+                        .findSimplestFalsification(initialValue) { it in passRange }
+
+                if (initialValue < 0) {
+                    assertEquals(-43, simplestValue)
+                } else {
+                    assertEquals(1338, simplestValue)
+                }
+            }
+    }
+}

settings.gradle.kts

@@ -9,11 +9,14 @@ include("generator-api")
 include("generator-stdlib")
 include("generator-test")
 
-include("evaluator")
 include("fuzzer-api")
+include("fuzzer-stdlib")
+
+include("evaluator")
 
 project(":generator-api").projectDir = file("generator/api")
 project(":generator-stdlib").projectDir = file("generator/stdlib")
 project(":generator-test").projectDir = file("generator/test")
 
 project(":fuzzer-api").projectDir = file("fuzzer/api")
+project(":fuzzer-stdlib").projectDir = file("fuzzer/stdlib")