Avoid spying collection-like types with @Spy if it may mislead @InjectMocks behaviour

utbot-framework-api/src/main/kotlin/org/utbot/framework/plugin/api/Api.kt

@@ -404,13 +404,10 @@ fun UtModel.isMockModel() = this is UtCompositeModel && isMock
  * Checks that this [UtModel] must be constructed with @Spy annotation in generated tests.
  * Used only for construct variables with @Spy annotation.
  */
-fun UtModel.canBeSpied(): Boolean {
-    val javaClass = this.classId.jClass
+fun UtModel.canBeSpied(): Boolean =
+    this is UtAssembleModel && spiedTypes.any { type -> type.isAssignableFrom(this.classId.jClass)}
 
-    return this is UtAssembleModel &&
-            (Collection::class.java.isAssignableFrom(javaClass)
-                    || Map::class.java.isAssignableFrom(javaClass))
-}
+val spiedTypes = setOf(Collection::class.java, Map::class.java)
 
 /**
  * Get model id (symbolic null value for UtNullModel)

utbot-spring-framework/src/main/kotlin/org/utbot/framework/codegen/tree/fieldmanager/CgSpiedFieldsManager.kt

@@ -1,5 +1,6 @@
 package org.utbot.framework.codegen.tree.fieldmanager
 
+import org.utbot.framework.codegen.domain.UtModelWrapper
 import org.utbot.framework.codegen.domain.builtin.spyClassId
 import org.utbot.framework.codegen.domain.context.CgContext
 import org.utbot.framework.codegen.domain.models.CgFieldDeclaration
@@ -12,6 +13,8 @@ import org.utbot.framework.plugin.api.UtAssembleModel
 import org.utbot.framework.plugin.api.UtModel
 import org.utbot.framework.plugin.api.canBeSpied
 import org.utbot.framework.plugin.api.isMockModel
+import org.utbot.framework.plugin.api.spiedTypes
+import org.utbot.framework.plugin.api.util.jClass
 
 class CgSpiedFieldsManager(context: CgContext) : CgAbstractClassFieldManager(context) {
 
@@ -38,10 +41,10 @@ class CgSpiedFieldsManager(context: CgContext) : CgAbstractClassFieldManager(con
                             cgModel !in dependentMockModels
                 }
 
-        return constructFieldsWithAnnotation(dependentSpyModels)
+        val suitableSpyModels = getSuitableSpyModels(dependentSpyModels)
+        return constructFieldsWithAnnotation(suitableSpyModels)
     }
 
-
     private val spyFrameworkManager = SpyFrameworkManager(context)
 
     override fun useVariableForModel(model: UtModel, variable: CgValue) {
@@ -57,4 +60,29 @@ class CgSpiedFieldsManager(context: CgContext) : CgAbstractClassFieldManager(con
         classId.canBeInjectedByTypeInto(classUnderTest)
 
     override fun constructBaseVarName(model: UtModel): String = super.constructBaseVarName(model) + "Spy"
+
+    private fun getSuitableSpyModels(potentialSpyModels: MutableSet<UtModelWrapper>): Set<UtModelWrapper> =
+        spiedTypes.fold(setOf()) { spyModels, type ->
+            spyModels + getSuitableSpyModelsOfType(type, potentialSpyModels)
+        }
+
+    /*
+     * Filters out cases when different tests use different [clazz]
+     * implementations and hence we need to inject different types.
+     *
+     * This limitation is reasoned by @InjectMocks behaviour.
+     * Otherwise, injection may be misleading:
+     * for example, several spies may be injected into one field.
+    */
+    private fun getSuitableSpyModelsOfType(
+        clazz: Class<*>,
+        potentialSpyModels: MutableSet<UtModelWrapper>
+    ): Set<UtModelWrapper> {
+        val spyModelsAssignableFrom = potentialSpyModels
+            .filter { clazz.isAssignableFrom(it.model.classId.jClass) }
+            .toSet()
+        val spyModelsTypesCount = spyModelsAssignableFrom.map { it.model.classId }.toSet().size
+
+        return if (spyModelsTypesCount == 1) spyModelsAssignableFrom else emptySet()
+    }
 }