Build: Fix test forks and memory calculations for low memory cases

buildSrc/src/main/kotlin/tasks.kt

@@ -183,7 +183,7 @@ fun Project.projectTest(
             project.kotlinBuildProperties.junit5NumberOfThreadsForParallelExecution ?: Runtime.getRuntime().availableProcessors()
 
         val memoryPerTestProcessMb = maxHeapSizeMb ?: if (jUnitMode == JUnitMode.JUnit5)
-            totalMaxMemoryForTestsMb.coerceAtMost(defaultMaxMemoryPerTestWorkerMb * junit5ParallelTestWorkers)
+            totalMaxMemoryForTestsMb.coerceIn(defaultMaxMemoryPerTestWorkerMb, defaultMaxMemoryPerTestWorkerMb * junit5ParallelTestWorkers)
         else
             defaultMaxMemoryPerTestWorkerMb
 
@@ -243,7 +243,7 @@ fun Project.projectTest(
             val forks = (totalMaxMemoryForTestsMb / memoryPerTestProcessMb).coerceAtMost(16)
             maxParallelForks =
                 project.providers.gradleProperty("kotlin.test.maxParallelForks").forUseAtConfigurationTime().orNull?.toInt()
-                    ?: forks.coerceAtMost(Runtime.getRuntime().availableProcessors())
+                    ?: forks.coerceIn(1, Runtime.getRuntime().availableProcessors())
         }
     }.apply { configure(body) }
 }

libraries/tools/kotlin-gradle-plugin-integration-tests/build.gradle.kts

@@ -201,7 +201,7 @@ if (isTeamcityBuild) {
 val KGP_TEST_TASKS_GROUP = "Kotlin Gradle Plugin Verification"
 val memoryPerGradleTestWorkerMb = 6000
 val maxParallelTestForks =
-    (totalMaxMemoryForTestsMb / memoryPerGradleTestWorkerMb).coerceAtMost(Runtime.getRuntime().availableProcessors())
+    (totalMaxMemoryForTestsMb / memoryPerGradleTestWorkerMb).coerceIn(1, Runtime.getRuntime().availableProcessors())
 
 val allParallelTestsTask = tasks.register<Test>("kgpAllParallelTests") {
     group = KGP_TEST_TASKS_GROUP