Update util methods collection in code generation taking into account multiple possible util method providers

Author: ArsenHD

utbot-framework/src/main/kotlin/org/utbot/framework/codegen/model/constructor/tree/CgTestClassConstructor.kt

@@ -4,6 +4,7 @@ import org.utbot.common.appendHtmlLine
 import org.utbot.engine.displayName
 import org.utbot.framework.codegen.ParametrizedTestSource
 import org.utbot.framework.codegen.model.constructor.CgMethodTestSet
+import org.utbot.framework.codegen.model.constructor.builtin.TestClassUtilMethodProvider
 import org.utbot.framework.codegen.model.constructor.context.CgContext
 import org.utbot.framework.codegen.model.constructor.context.CgContextOwner
 import org.utbot.framework.codegen.model.constructor.util.CgComponents
@@ -67,8 +68,10 @@ internal class CgTestClassConstructor(val context: CgContext) :
                         staticDeclarationRegions += CgStaticsRegion("Data providers", cgDataProviderMethods)
                     }
 
-                    val utilMethods = createUtilMethods()
-                    if (utilMethods.isNotEmpty()) {
+                    val utilMethods = collectUtilMethods()
+                    // If utilMethodProvider is TestClassUtilMethodProvider, then util methods should be declared
+                    // in the test class. Otherwise, util methods will be located elsewhere (e.g. another class or library).
+                    if (utilMethodProvider is TestClassUtilMethodProvider && utilMethods.isNotEmpty()) {
                         staticDeclarationRegions += CgStaticsRegion("Util methods", utilMethods)
                     }
                 }
@@ -164,8 +167,17 @@ internal class CgTestClassConstructor(val context: CgContext) :
         }.onFailure { error -> processFailure(testSet, error) }
     }
 
-    // TODO: collect imports of util methods
-    private fun createUtilMethods(): List<CgUtilMethod> {
+    /**
+     * This method collects a list of util methods needed by the class.
+     * By the end of the test method generation [requiredUtilMethods] may not contain all the methods needed.
+     * That's because some util methods may not be directly used in tests, but they may be used from other util methods.
+     * We define such method dependencies in [MethodId.dependencies].
+     *
+     * Once all dependencies are collected, they are also added to [requiredUtilMethods].
+     *
+     * @return a list of [CgUtilMethod] representing required util methods (including dependencies).
+     */
+    private fun collectUtilMethods(): List<CgUtilMethod> {
         val utilMethods = mutableListOf<CgUtilMethod>()
         // some util methods depend on the others
         // using this loop we make sure that all the
@@ -175,11 +187,18 @@ internal class CgTestClassConstructor(val context: CgContext) :
             requiredUtilMethods.remove(method)
             if (method.name !in existingMethodNames) {
                 utilMethods += CgUtilMethod(method)
-                importUtilMethodDependencies(method)
+                // we only need imports from util methods if these util methods are declared in the test class
+                if (utilMethodProvider is TestClassUtilMethodProvider) {
+                    importUtilMethodDependencies(method)
+                }
                 existingMethodNames += method.name
                 requiredUtilMethods += method.dependencies()
             }
         }
+        // Collect all util methods back into requiredUtilMethods.
+        // Now there will also be util methods that weren't present in requiredUtilMethods at first,
+        // but were needed for the present util methods to work.
+        requiredUtilMethods += utilMethods.map { method -> method.id }
         return utilMethods
     }