Support mock strategies and type replacement in Spring unit test fuzzing (#2561)

* Support mock strategies and type replacement in Spring unit test fuzzing

* Avoid mocking replaced types

* Only use `InjectMockValueProvider` for `thisInstance`

* Disallow non-mocks when mock can be used

* Move all value provider decorators to one package

* Improve adding of `ReplacedFuzzedTypeFlag`

* Make `map` and `except` apply transformer/filter to ALL value providers

* Avoid using `anyObjectValueProvider` that is removed in #2583

* Make `AnyObjectValueProvider` not extend any interfaces, remove unrelated comment

* Fix compilation after rebase

Author: IlyaMuravjov

utbot-framework/src/main/kotlin/org/utbot/engine/Traverser.kt

@@ -1397,7 +1397,7 @@ class Traverser(
         // from Spring bean definitions, for example), we can just create a symbolic object
         // with hard constraint on the mentioned type.
         val replacedClassId = when (typeReplacer.typeReplacementMode) {
-            KnownImplementor -> typeReplacer.replaceTypeIfNeeded(type)
+            KnownImplementor -> typeReplacer.replaceTypeIfNeeded(type.id)
             AnyImplementor,
             NoImplementors -> null
         }

utbot-framework/src/main/kotlin/org/utbot/engine/UtBotSymbolicEngine.kt

@@ -424,7 +424,6 @@ class UtBotSymbolicEngine(
      * Run fuzzing flow.
      *
      * @param until is used by fuzzer to cancel all tasks if the current time is over this value
-     * @param transform provides model values for a method
      */
     fun fuzzing(until: Long = Long.MAX_VALUE) = flow {
         val isFuzzable = methodUnderTest.parameters.all { classId ->

utbot-framework/src/main/kotlin/org/utbot/framework/context/TypeReplacer.kt

@@ -2,7 +2,6 @@ package org.utbot.framework.context
 
 import org.utbot.framework.plugin.api.ClassId
 import org.utbot.framework.plugin.api.TypeReplacementMode
-import soot.RefType
 
 interface TypeReplacer {
     /**
@@ -14,5 +13,5 @@ interface TypeReplacer {
      * Finds a type to replace the original abstract type
      * if it is guided with some additional information.
      */
-    fun replaceTypeIfNeeded(type: RefType): ClassId?
+    fun replaceTypeIfNeeded(classId: ClassId): ClassId?
 }

utbot-framework/src/main/kotlin/org/utbot/framework/context/custom/MockingJavaFuzzingContext.kt

@@ -1,41 +1,51 @@
 package org.utbot.framework.context.custom
 
 import org.utbot.framework.context.JavaFuzzingContext
+import org.utbot.framework.plugin.api.UtNullModel
 import org.utbot.framework.plugin.api.ExecutableId
+import org.utbot.fuzzer.FuzzedType
 import org.utbot.fuzzing.JavaValueProvider
-import org.utbot.fuzzing.providers.MapValueProvider
+import org.utbot.fuzzing.Seed
+import org.utbot.fuzzing.providers.AnyDepthNullValueProvider
+import org.utbot.fuzzing.providers.AnyObjectValueProvider
 import org.utbot.fuzzing.spring.unit.MockValueProvider
-import org.utbot.fuzzing.providers.NullValueProvider
-import org.utbot.fuzzing.providers.ObjectValueProvider
-import org.utbot.fuzzing.providers.StringValueProvider
+import org.utbot.fuzzing.spring.decorators.filterSeeds
+import org.utbot.fuzzing.spring.decorators.filterTypes
 import org.utbot.instrumentation.instrumentation.execution.UtConcreteExecutionResult
 
 /**
- * Makes fuzzer mock all types that don't have *specific* [JavaValueProvider],
- * like [MapValueProvider] or [StringValueProvider].
+ * Makes fuzzer to use mocks in accordance with [mockPredicate].
  *
- * NOTE: the caller is responsible for providing some *specific* [JavaValueProvider]
- *       that can create values for class under test (otherwise it will be mocked),
- *       [ObjectValueProvider] and [NullValueProvider] do not count as *specific*.
+ * NOTE:
+ *   - fuzzer won't mock types, that have *specific* value providers
+ *   (i.e. ones that do not implement [AnyObjectValueProvider])
+ *   - fuzzer may still resort to mocks despite [mockPredicate] and *specific*
+ *   value providers if it can't create other non-null values or at runtime
  */
-fun JavaFuzzingContext.mockAllTypesWithoutSpecificValueProvider() =
-    MockingJavaFuzzingContext(delegateContext = this)
+fun JavaFuzzingContext.useMocks(mockPredicate: (FuzzedType) -> Boolean) =
+    MockingJavaFuzzingContext(delegateContext = this, mockPredicate)
 
 class MockingJavaFuzzingContext(
-    val delegateContext: JavaFuzzingContext
+    val delegateContext: JavaFuzzingContext,
+    val mockPredicate: (FuzzedType) -> Boolean,
 ) : JavaFuzzingContext by delegateContext {
     private val mockValueProvider = MockValueProvider(delegateContext.idGenerator)
 
     override val valueProvider: JavaValueProvider =
-        // NOTE: we first remove `NullValueProvider` from `delegateContext.valueProvider` and then
-        //       add it back as a part of our `withFallback` so it has the same priority as
-        //       `mockValueProvider`, otherwise mocks will never be used where `null` can be used.
+
         delegateContext.valueProvider
-            .except { it is NullValueProvider }
-            .except { it is ObjectValueProvider }
+            // NOTE: we first remove `AnyObjectValueProvider` and `NullValueProvider` from `delegateContext.valueProvider`
+            //       and then add them back as a part of our `withFallback` so they have the same priority as
+            //       `mockValueProvider`, otherwise mocks will never be used where `null` or new object can be used.
+            .except { it is AnyObjectValueProvider }
             .withFallback(
-                mockValueProvider
-                    .with(NullValueProvider)
+                mockValueProvider.filterTypes(mockPredicate)
+                    .with(
+                        delegateContext.valueProvider
+                            .filterTypes { !mockPredicate(it) }
+                            .filterSeeds { (it as? Seed.Simple)?.value?.model !is UtNullModel  }
+                    )
+                    .withFallback(mockValueProvider.with(AnyDepthNullValueProvider))
             )
 
     override fun handleFuzzedConcreteExecutionResult(

utbot-framework/src/main/kotlin/org/utbot/framework/context/simple/SimpleTypeReplacer.kt

@@ -3,10 +3,9 @@ package org.utbot.framework.context.simple
 import org.utbot.framework.context.TypeReplacer
 import org.utbot.framework.plugin.api.ClassId
 import org.utbot.framework.plugin.api.TypeReplacementMode
-import soot.RefType
 
 class SimpleTypeReplacer : TypeReplacer {
     override val typeReplacementMode: TypeReplacementMode = TypeReplacementMode.AnyImplementor
 
-    override fun replaceTypeIfNeeded(type: RefType): ClassId? = null
+    override fun replaceTypeIfNeeded(classId: ClassId): ClassId? = null
 }

utbot-fuzzing/src/main/kotlin/org/utbot/fuzzing/Providers.kt

@@ -92,26 +92,16 @@ fun interface ValueProvider<T, R, D : Description<T>> {
     }
 
     /**
-     * Removes `anotherValueProviders<T, R` from current one.
+     * Removes providers matching [filter] from the current one.
      */
-    fun except(filter: (ValueProvider<T, R, D>) -> Boolean): ValueProvider<T, R, D> {
-        return if (this is Combined) {
-            Combined(providers.map { it.unwrapIfFallback() }.filterNot(filter))
-        } else {
-            Combined(if (filter(unwrapIfFallback())) emptyList() else listOf(this))
-        }
-    }
+    fun except(filter: (ValueProvider<T, R, D>) -> Boolean): ValueProvider<T, R, D> =
+        map { if (filter(it)) Combined(emptyList()) else it }
 
     /**
      * Applies [transform] for current provider
      */
-    fun map(transform: (ValueProvider<T, R, D>) -> ValueProvider<T, R, D>): ValueProvider<T, R, D> {
-        return if (this is Combined) {
-            Combined(providers.map(transform))
-        } else {
-            transform(this)
-        }
-    }
+    fun map(transform: (ValueProvider<T, R, D>) -> ValueProvider<T, R, D>): ValueProvider<T, R, D> =
+        transform(this)
 
     /**
      * Uses fallback value provider in case when 'this' one failed to generate any value.
@@ -167,6 +157,8 @@ fun interface ValueProvider<T, R, D : Description<T>> {
             }
         }
 
+        override fun map(transform: (ValueProvider<T, R, D>) -> ValueProvider<T, R, D>): ValueProvider<T, R, D> =
+            transform(Fallback(provider.map(transform), fallback.map(transform)))
     }
 
     /**
@@ -200,6 +192,9 @@ fun interface ValueProvider<T, R, D : Description<T>> {
                 }
             }
         }
+
+        override fun map(transform: (ValueProvider<T, R, D>) -> ValueProvider<T, R, D>): ValueProvider<T, R, D> =
+            transform(Combined(providers.map { it.map(transform) }))
     }
 
     companion object {

utbot-java-fuzzing/src/main/kotlin/org/utbot/fuzzing/JavaLanguage.kt

@@ -171,7 +171,7 @@ internal fun FuzzedType.traverseHierarchy(typeCache: MutableMap<Type, FuzzedType
  * @param type to be resolved
  * @param cache is used to store same [FuzzedType] for same java types
  */
-internal fun toFuzzerType(type: Type, cache: MutableMap<Type, FuzzedType>): FuzzedType {
+fun toFuzzerType(type: Type, cache: MutableMap<Type, FuzzedType>): FuzzedType {
     return toFuzzerType(
         type = type,
         classId = { t -> toClassId(t, cache) },

utbot-java-fuzzing/src/main/kotlin/org/utbot/fuzzing/providers/Objects.kt

@@ -70,9 +70,16 @@ fun anyObjectValueProvider(idGenerator: IdentityPreservingIdGenerator<Int>) =
         ovp.withFallback(AbstractsObjectValueProvider(idGenerator))
     }
 
+/**
+ * Marker interface that shows that this [JavaValueProvider] can potentially provide values of
+ * arbitrary types, unlike type-specific value providers that were designed to provide values of
+ * few specific popular types (e.g. `List`, `String`, etc.).
+ */
+interface AnyObjectValueProvider
+
 class ObjectValueProvider(
     val idGenerator: IdGenerator<Int>,
-) : JavaValueProvider {
+) : JavaValueProvider, AnyObjectValueProvider {
 
     override fun accept(type: FuzzedType) = !isIgnored(type.classId)
 
@@ -140,7 +147,7 @@ class ObjectValueProvider(
 }
 
 @Suppress("unused")
-object NullValueProvider : JavaValueProvider {
+object NullValueProvider : JavaValueProvider, AnyObjectValueProvider {
 
     override fun enrich(description: FuzzedDescription, type: FuzzedType, scope: Scope) {
         // any value in static function is ok to fuzz
@@ -170,7 +177,7 @@ object NullValueProvider : JavaValueProvider {
  *
  * Intended to be used as a last fallback.
  */
-object AnyDepthNullValueProvider : JavaValueProvider {
+object AnyDepthNullValueProvider : JavaValueProvider, AnyObjectValueProvider {
 
     override fun accept(type: FuzzedType) = type.classId.isRefType
 
@@ -185,7 +192,7 @@ object AnyDepthNullValueProvider : JavaValueProvider {
  */
 class AbstractsObjectValueProvider(
     val idGenerator: IdGenerator<Int>,
-) : JavaValueProvider {
+) : JavaValueProvider, AnyObjectValueProvider {
 
     override fun accept(type: FuzzedType) = type.classId.isRefType && !isKnownTypes(type.classId)
 

utbot-java-fuzzing/src/main/kotlin/org/utbot/fuzzing/providers/ModifyingWithMethodsProviderWrapper.kt renamed to utbot-java-fuzzing/src/main/kotlin/org/utbot/fuzzing/spring/decorators/ModifyingWithMethodsProviderWrapper.kt

@@ -1,4 +1,4 @@
-package org.utbot.fuzzing.providers
+package org.utbot.fuzzing.spring.decorators
 
 import org.utbot.framework.plugin.api.ClassId
 import org.utbot.framework.plugin.api.UtAssembleModel
@@ -9,8 +9,8 @@ import org.utbot.fuzzer.FuzzedValue
 import org.utbot.fuzzing.FuzzedDescription
 import org.utbot.fuzzing.JavaValueProvider
 import org.utbot.fuzzing.Routine
-import org.utbot.fuzzing.Scope
 import org.utbot.fuzzing.Seed
+import org.utbot.fuzzing.providers.findMethodsToModifyWith
 
 /**
  * Value provider that is a buddy for another provider
@@ -22,8 +22,11 @@ import org.utbot.fuzzing.Seed
  */
 class ModifyingWithMethodsProviderWrapper(
     private val classUnderTest: ClassId,
-    private val delegate: JavaValueProvider
-) : JavaValueProvider by delegate {
+    delegate: JavaValueProvider
+) : ValueProviderDecorator<FuzzedType, FuzzedValue, FuzzedDescription>(delegate) {
+
+    override fun wrap(provider: JavaValueProvider): JavaValueProvider =
+        ModifyingWithMethodsProviderWrapper(classUnderTest, provider)
 
     override fun generate(description: FuzzedDescription, type: FuzzedType): Sequence<Seed<FuzzedType, FuzzedValue>> =
         delegate
@@ -50,9 +53,4 @@ class ModifyingWithMethodsProviderWrapper(
                     )
                 } else seed
             }
-
-    override fun enrich(description: FuzzedDescription, type: FuzzedType, scope: Scope) =
-        delegate.enrich(description, type, scope)
-
-    override fun accept(type: FuzzedType): Boolean = delegate.accept(type)
 }

utbot-java-fuzzing/src/main/kotlin/org/utbot/fuzzing/spring/PropertyPreservingValueProvider.kt renamed to utbot-java-fuzzing/src/main/kotlin/org/utbot/fuzzing/spring/decorators/PropertyPreservingValueProvider.kt

@@ -1,13 +1,15 @@
-package org.utbot.fuzzing.spring
+package org.utbot.fuzzing.spring.decorators
 
 import org.utbot.common.toDynamicProperties
 import org.utbot.fuzzer.FuzzedType
 import org.utbot.fuzzer.FuzzedValue
 import org.utbot.fuzzing.FuzzedDescription
 import org.utbot.fuzzing.JavaValueProvider
 import org.utbot.fuzzing.Routine
-import org.utbot.fuzzing.Scope
 import org.utbot.fuzzing.Seed
+import org.utbot.fuzzing.spring.FuzzedTypeProperty
+import org.utbot.fuzzing.spring.addProperties
+import org.utbot.fuzzing.spring.properties
 
 /**
  * @see preserveProperties
@@ -25,14 +27,14 @@ interface PreservableFuzzedTypeProperty<T> : FuzzedTypeProperty<T>
 fun JavaValueProvider.preserveProperties() : JavaValueProvider =
     PropertyPreservingValueProvider(this)
 
-class PropertyPreservingValueProvider(private val delegateProvider: JavaValueProvider) : JavaValueProvider {
-    override fun enrich(description: FuzzedDescription, type: FuzzedType, scope: Scope) =
-        delegateProvider.enrich(description, type, scope)
-
-    override fun accept(type: FuzzedType): Boolean = delegateProvider.accept(type)
+class PropertyPreservingValueProvider(
+    delegate: JavaValueProvider
+) : ValueProviderDecorator<FuzzedType, FuzzedValue, FuzzedDescription>(delegate) {
+    override fun wrap(provider: JavaValueProvider): JavaValueProvider =
+        provider.preserveProperties()
 
     override fun generate(description: FuzzedDescription, type: FuzzedType): Sequence<Seed<FuzzedType, FuzzedValue>> {
-        val delegateSeeds = delegateProvider.generate(description, type)
+        val delegateSeeds = delegate.generate(description, type)
 
         val preservedProperties = type.properties.entries
             .filter { it.property is PreservableFuzzedTypeProperty }
@@ -67,10 +69,4 @@ class PropertyPreservingValueProvider(private val delegateProvider: JavaValuePro
             }
         }
     }
-
-    override fun map(transform: (JavaValueProvider) -> JavaValueProvider): JavaValueProvider =
-        delegateProvider.map(transform).preserveProperties()
-
-    override fun except(filter: (JavaValueProvider) -> Boolean): JavaValueProvider =
-        delegateProvider.except(filter).preserveProperties()
 }

utbot-java-fuzzing/src/main/kotlin/org/utbot/fuzzing/spring/decorators/SeedFilteringValueProvider.kt

@@ -0,0 +1,19 @@
+package org.utbot.fuzzing.spring.decorators
+
+import org.utbot.fuzzing.Description
+import org.utbot.fuzzing.Seed
+import org.utbot.fuzzing.ValueProvider
+
+fun <T, R, D : Description<T>> ValueProvider<T, R, D>.filterSeeds(predicate: (Seed<T, R>) -> Boolean) =
+    SeedFilteringValueProvider(delegate = this, predicate)
+
+class SeedFilteringValueProvider<T, R, D : Description<T>>(
+    delegate: ValueProvider<T, R, D>,
+    private val predicate: (Seed<T, R>) -> Boolean
+) : ValueProviderDecorator<T, R, D>(delegate) {
+    override fun wrap(provider: ValueProvider<T, R, D>): ValueProvider<T, R, D> =
+        provider.filterSeeds(predicate)
+
+    override fun generate(description: D, type: T): Sequence<Seed<T, R>> =
+        delegate.generate(description, type).filter(predicate)
+}

utbot-java-fuzzing/src/main/kotlin/org/utbot/fuzzing/spring/decorators/TypeFilteringValueProvider.kt

@@ -0,0 +1,18 @@
+package org.utbot.fuzzing.spring.decorators
+
+import org.utbot.fuzzing.Description
+import org.utbot.fuzzing.ValueProvider
+
+fun <T, R, D : Description<T>> ValueProvider<T, R, D>.filterTypes(predicate: (T) -> Boolean) =
+    TypeFilteringValueProvider(delegate = this, predicate)
+
+class TypeFilteringValueProvider<T, R, D : Description<T>>(
+    delegate: ValueProvider<T, R, D>,
+    private val predicate: (T) -> Boolean
+) : ValueProviderDecorator<T, R, D>(delegate) {
+    override fun wrap(provider: ValueProvider<T, R, D>): ValueProvider<T, R, D> =
+        provider.filterTypes(predicate)
+
+    override fun accept(type: T): Boolean =
+        predicate(type) && super.accept(type)
+}

utbot-java-fuzzing/src/main/kotlin/org/utbot/fuzzing/spring/decorators/TypeReplacingValueProvider.kt

@@ -0,0 +1,28 @@
+package org.utbot.fuzzing.spring.decorators
+
+import org.utbot.fuzzing.Description
+import org.utbot.fuzzing.Scope
+import org.utbot.fuzzing.Seed
+import org.utbot.fuzzing.ValueProvider
+
+fun <T, R, D : Description<T>> ValueProvider<T, R, D>.replaceTypes(typeReplacer: (D, T) -> T) =
+    TypeReplacingValueProvider(delegate = this, typeReplacer)
+
+class TypeReplacingValueProvider<T, R, D : Description<T>>(
+    delegate: ValueProvider<T, R, D>,
+    private val typeReplacer: (D, T) -> T
+) : ValueProviderDecorator<T, R, D>(delegate) {
+    override fun wrap(provider: ValueProvider<T, R, D>): ValueProvider<T, R, D> =
+        provider.replaceTypes(typeReplacer)
+
+    override fun enrich(description: D, type: T, scope: Scope) =
+        super.enrich(description, typeReplacer(description, type), scope)
+
+    override fun accept(type: T): Boolean = true
+
+    override fun generate(description: D, type: T): Sequence<Seed<T, R>> =
+        if (super.accept(typeReplacer(description, type)))
+            super.generate(description, typeReplacer(description, type))
+        else
+            emptySequence()
+}