diff --git a/platform/external-system-impl/intellij.platform.externalSystem.tests.iml b/platform/external-system-impl/intellij.platform.externalSystem.tests.iml
index d81cbf7e5565..3553348b2048 100644
--- a/platform/external-system-impl/intellij.platform.externalSystem.tests.iml
+++ b/platform/external-system-impl/intellij.platform.externalSystem.tests.iml
@@ -22,5 +22,6 @@
     <orderEntry type="library" scope="TEST" name="JUnit4" level="project" />
     <orderEntry type="library" scope="TEST" name="assertJ" level="project" />
     <orderEntry type="library" scope="TEST" name="mockito" level="project" />
+    <orderEntry type="module" module-name="intellij.platform.lang.tests" scope="TEST" />
   </component>
 </module>
\ No newline at end of file
diff --git a/platform/external-system-impl/src/com/intellij/openapi/externalSystem/service/execution/ExternalSystemJdkUtil.java b/platform/external-system-impl/src/com/intellij/openapi/externalSystem/service/execution/ExternalSystemJdkUtil.java
index 4936632eb96c..95de8a0f0f29 100644
--- a/platform/external-system-impl/src/com/intellij/openapi/externalSystem/service/execution/ExternalSystemJdkUtil.java
+++ b/platform/external-system-impl/src/com/intellij/openapi/externalSystem/service/execution/ExternalSystemJdkUtil.java
@@ -7,6 +7,7 @@ import com.intellij.openapi.module.ModuleManager;
 import com.intellij.openapi.project.Project;
 import com.intellij.openapi.projectRoots.*;
 import com.intellij.openapi.projectRoots.impl.DependentSdkType;
+import com.intellij.openapi.projectRoots.impl.MockSdk;
 import com.intellij.openapi.projectRoots.impl.SdkConfigurationUtil;
 import com.intellij.openapi.roots.ModuleRootManager;
 import com.intellij.openapi.roots.ProjectRootManager;
diff --git a/platform/external-system-impl/src/com/intellij/openapi/externalSystem/service/ui/ExternalSystemJdkComboBoxUtil.kt b/platform/external-system-impl/src/com/intellij/openapi/externalSystem/service/ui/ExternalSystemJdkComboBoxUtil.kt
index ed574cbcb004..c79e20ce653e 100644
--- a/platform/external-system-impl/src/com/intellij/openapi/externalSystem/service/ui/ExternalSystemJdkComboBoxUtil.kt
+++ b/platform/external-system-impl/src/com/intellij/openapi/externalSystem/service/ui/ExternalSystemJdkComboBoxUtil.kt
@@ -5,36 +5,38 @@ package com.intellij.openapi.externalSystem.service.ui
 
 import com.intellij.openapi.externalSystem.service.execution.ExternalSystemJdkException
 import com.intellij.openapi.externalSystem.service.execution.ExternalSystemJdkUtil
+import com.intellij.openapi.externalSystem.service.execution.ExternalSystemJdkUtil.USE_PROJECT_JDK
 import com.intellij.openapi.projectRoots.Sdk
 import com.intellij.openapi.projectRoots.impl.SdkConfigurationUtil
 import com.intellij.openapi.roots.ui.configuration.SdkComboBox
 import com.intellij.openapi.roots.ui.configuration.SdkListItem
+import org.jetbrains.annotations.TestOnly
 
-fun SdkComboBox.getSelectedJdkReference(): String? {
-  return when (val it = selectedItem) {
-    is SdkListItem.ProjectSdkItem -> ExternalSystemJdkUtil.USE_PROJECT_JDK
-    is SdkListItem.SdkItem -> it.sdk.name
-    is SdkListItem.InvalidSdkItem -> it.sdkName
+fun SdkComboBox.getSelectedJdkReference() = resolveJdkReference(selectedItem)
+
+private fun resolveJdkReference(item: SdkListItem?): String? {
+  return when (item) {
+    is SdkListItem.ProjectSdkItem -> USE_PROJECT_JDK
+    is SdkListItem.SdkItem -> item.sdk.name
+    is SdkListItem.InvalidSdkItem -> item.sdkName
     else -> null
   }
 }
 
 fun SdkComboBox.setSelectedJdkReference(jdkReference: String?) {
-  selectedItem = when (jdkReference) {
-    null -> showNoneSdkItem()
-    ExternalSystemJdkUtil.USE_PROJECT_JDK -> showProjectSdkItem()
-    else -> resolveSdkItem(jdkReference)
-  }
+  selectedItem = resolveSdkItem(jdkReference)
 }
 
-private fun SdkComboBox.resolveSdkItem(selectedJdkReference: String): SdkListItem {
+private fun SdkComboBox.resolveSdkItem(jdkReference: String?): SdkListItem {
+  if (jdkReference == null) return showNoneSdkItem()
+  if (jdkReference == USE_PROJECT_JDK) return showProjectSdkItem()
   try {
-    val selectedJdk = ExternalSystemJdkUtil.resolveJdkName(null, selectedJdkReference)
-    if (selectedJdk == null) return showInvalidSdkItem(selectedJdkReference)
+    val selectedJdk = ExternalSystemJdkUtil.resolveJdkName(null, jdkReference)
+    if (selectedJdk == null) return showInvalidSdkItem(jdkReference)
     return findSdkItem(selectedJdk) ?: addAndGetSdkItem(selectedJdk)
   }
   catch (ex: ExternalSystemJdkException) {
-    return showInvalidSdkItem(selectedJdkReference)
+    return showInvalidSdkItem(jdkReference)
   }
 }
 
@@ -47,4 +49,7 @@ private fun SdkComboBox.addAndGetSdkItem(sdk: Sdk): SdkListItem {
 
 private fun SdkComboBox.findSdkItem(sdk: Sdk): SdkListItem? {
   return model.listModel.findSdkItem(sdk)
-}
\ No newline at end of file
+}
+
+@TestOnly
+fun resolveJdkReferenceInTests(item: SdkListItem?) = resolveJdkReference(item)
diff --git a/platform/external-system-impl/testSrc/com/intellij/openapi/externalSystem/service/ui/ExternalSystemJdkComboBoxUtilTest.kt b/platform/external-system-impl/testSrc/com/intellij/openapi/externalSystem/service/ui/ExternalSystemJdkComboBoxUtilTest.kt
new file mode 100644
index 000000000000..5ff076cda429
--- /dev/null
+++ b/platform/external-system-impl/testSrc/com/intellij/openapi/externalSystem/service/ui/ExternalSystemJdkComboBoxUtilTest.kt
@@ -0,0 +1,50 @@
+// Copyright 2000-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package com.intellij.openapi.externalSystem.service.ui
+
+import com.intellij.openapi.externalSystem.service.execution.ExternalSystemJdkUtil.USE_INTERNAL_JAVA
+import com.intellij.openapi.externalSystem.service.execution.ExternalSystemJdkUtil.USE_PROJECT_JDK
+import com.intellij.openapi.roots.ui.configuration.SdkListItem.*
+
+class ExternalSystemJdkComboBoxUtilTest : ExternalSystemJdkComboBoxUtilTestCase() {
+  fun `test reference usage`() {
+    val sdk1 = createAndRegisterSdk()
+    val sdk2 = createAndRegisterSdk(isProjectSdk = true)
+    val sdk3 = createAndRegisterSdk()
+    val invalidSdk = TestSdkGenerator.createNextSdk()
+    val internalJdk = getInternalJdk()
+
+    val comboBox = createJdkComboBox()
+
+    assertComboBoxContent(comboBox)
+      .reference(USE_PROJECT_JDK)
+      .reference(sdk1)
+      .reference(sdk2)
+      .reference(sdk3)
+      .nothing()
+
+    comboBox.setSelectedJdkReference(USE_PROJECT_JDK)
+    assertComboBoxSelection<ProjectSdkItem>(comboBox, sdk2, USE_PROJECT_JDK)
+    comboBox.setSelectedJdkReference(sdk1.name)
+    assertComboBoxSelection<SdkItem>(comboBox, sdk1, sdk1.name)
+    comboBox.setSelectedJdkReference(sdk2.name)
+    assertComboBoxSelection<SdkItem>(comboBox, sdk2, sdk2.name)
+    comboBox.setSelectedJdkReference(sdk3.name)
+    assertComboBoxSelection<SdkItem>(comboBox, sdk3, sdk3.name)
+    comboBox.setSelectedJdkReference(invalidSdk.name)
+    assertComboBoxSelection<InvalidSdkItem>(comboBox, null, invalidSdk.name)
+    comboBox.setSelectedJdkReference(USE_INTERNAL_JAVA)
+    assertComboBoxSelection<SdkItem>(comboBox, internalJdk, internalJdk.name)
+    comboBox.setSelectedJdkReference(null)
+    assertComboBoxSelection<NoneSdkItem>(comboBox, null, null)
+
+    assertComboBoxContent(comboBox)
+      .reference(null, isSelected = true)
+      .reference(USE_PROJECT_JDK)
+      .reference(invalidSdk.name)
+      .reference(internalJdk)
+      .reference(sdk1)
+      .reference(sdk2)
+      .reference(sdk3)
+      .nothing()
+  }
+}
\ No newline at end of file
diff --git a/platform/external-system-impl/testSrc/com/intellij/openapi/externalSystem/service/ui/ExternalSystemJdkComboBoxUtilTestCase.kt b/platform/external-system-impl/testSrc/com/intellij/openapi/externalSystem/service/ui/ExternalSystemJdkComboBoxUtilTestCase.kt
new file mode 100644
index 000000000000..0a7ba2a54405
--- /dev/null
+++ b/platform/external-system-impl/testSrc/com/intellij/openapi/externalSystem/service/ui/ExternalSystemJdkComboBoxUtilTestCase.kt
@@ -0,0 +1,40 @@
+// Copyright 2000-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package com.intellij.openapi.externalSystem.service.ui
+
+import com.intellij.openapi.application.invokeAndWaitIfNeeded
+import com.intellij.openapi.application.runWriteAction
+import com.intellij.openapi.projectRoots.JavaSdkType
+import com.intellij.openapi.projectRoots.Sdk
+import com.intellij.openapi.projectRoots.impl.JavaAwareProjectJdkTableImpl
+import com.intellij.openapi.roots.ui.configuration.SdkComboBox
+import com.intellij.openapi.roots.ui.configuration.SdkComboBoxTestCase
+import com.intellij.openapi.roots.ui.configuration.SdkListItem
+
+abstract class ExternalSystemJdkComboBoxUtilTestCase : SdkComboBoxTestCase() {
+
+  override fun tearDown() {
+    invokeAndWaitIfNeeded {
+      runWriteAction {
+        JavaAwareProjectJdkTableImpl.removeInternalJdkInTests()
+      }
+    }
+    super.tearDown()
+  }
+
+  fun createJdkComboBox() = createComboBox { it is JavaSdkType }
+
+  fun ComboBoxChecker.reference(sdk: Sdk, isSelected: Boolean = false) =
+    reference(sdk.name, isSelected)
+
+  fun ComboBoxChecker.reference(reference: String?, isSelected: Boolean = false) =
+    item<SdkListItem>(isSelected) {
+      assertEquals(reference, resolveJdkReferenceInTests(it))
+    }
+
+  fun getInternalJdk() = JavaAwareProjectJdkTableImpl.getInstanceEx().internalJdk
+
+  inline fun <reified I : SdkListItem> assertComboBoxSelection(comboBox: SdkComboBox, expectedSdk: Sdk?, expectedReference: String?) {
+    assertComboBoxSelection<I>(comboBox, expectedSdk)
+    assertEquals(expectedReference, comboBox.getSelectedJdkReference())
+  }
+}
\ No newline at end of file
diff --git a/platform/lang-impl/src/com/intellij/openapi/roots/ui/configuration/SdkComboBox.kt b/platform/lang-impl/src/com/intellij/openapi/roots/ui/configuration/SdkComboBox.kt
index b9995da28be5..54ac3d7c4eb7 100644
--- a/platform/lang-impl/src/com/intellij/openapi/roots/ui/configuration/SdkComboBox.kt
+++ b/platform/lang-impl/src/com/intellij/openapi/roots/ui/configuration/SdkComboBox.kt
@@ -15,12 +15,21 @@ class SdkComboBox(model: SdkComboBoxModel) : SdkComboBoxBase<SdkListItem>(model.
     setModel(model.copyAndSetListModel(listModel))
   }
 
+  override fun getSelectedItem(): SdkListItem? {
+    return super.getSelectedItem() as SdkListItem?
+  }
+
   override fun setSelectedItem(anObject: Any?) {
     if (anObject is SdkListItem) {
       if (myModel.executeAction(this, anObject, ::setSelectedItem)) {
         return
       }
     }
+    when (anObject) {
+      is SdkListItem.ProjectSdkItem -> showProjectSdkItem()
+      is SdkListItem.InvalidSdkItem -> showInvalidSdkItem(anObject.sdkName)
+      is SdkListItem.NoneSdkItem -> showNoneSdkItem()
+    }
     reloadModel()
     super.setSelectedItem(anObject)
   }
@@ -37,12 +46,14 @@ class SdkComboBox(model: SdkComboBoxModel) : SdkComboBoxBase<SdkListItem>(model.
 
   fun getSelectedSdk(): Sdk? {
     return when (val it = selectedItem) {
-      is SdkListItem.ProjectSdkItem -> model.sdksModel.projectSdk
-      is SdkListItem.SdkItem -> it.sdk
+      is SdkListItem.ProjectSdkItem -> findSdk(model.sdksModel.projectSdk)
+      is SdkListItem.SdkItem -> findSdk(it.sdk)
       else -> null
     }
   }
 
+  private fun findSdk(sdk: Sdk?) = model.sdksModel.findSdk(sdk)
+
   init {
     setModel(model)
     setRenderer(SdkListPresenter { this@SdkComboBox.model.listModel })
diff --git a/platform/lang-impl/src/com/intellij/openapi/roots/ui/configuration/SdkDetector.java b/platform/lang-impl/src/com/intellij/openapi/roots/ui/configuration/SdkDetector.java
index 63fceeca8bdc..fd3ae74d71c1 100644
--- a/platform/lang-impl/src/com/intellij/openapi/roots/ui/configuration/SdkDetector.java
+++ b/platform/lang-impl/src/com/intellij/openapi/roots/ui/configuration/SdkDetector.java
@@ -2,6 +2,7 @@
 package com.intellij.openapi.roots.ui.configuration;
 
 import com.intellij.openapi.Disposable;
+import com.intellij.openapi.application.Application;
 import com.intellij.openapi.application.ApplicationManager;
 import com.intellij.openapi.application.ModalityState;
 import com.intellij.openapi.diagnostic.Logger;
@@ -58,6 +59,17 @@ public class SdkDetector {
       return;
     }
 
+    /*
+      TODO[jo] fix: deadlock in combobox tests on {@link SdkDetector#myPublicationLock}
+       detection must be called from edt {@link SdkDetector#getDetectedSdksWithUpdate}
+       detection is synchronous for unit tests {@link com.intellij.openapi.progress.impl.CoreProgressManager#run}
+     */
+    Application application = ApplicationManager.getApplication();
+    if (application.isUnitTestMode() || application.isHeadlessEnvironment()) {
+      LOG.warn("Sdks detection is skipped, because deadlock is coming for synchronous detection");
+      return;
+    }
+
     EdtDetectedSdkListener actualListener = new EdtDetectedSdkListener(callbackModality, listener);
     synchronized (myPublicationLock) {
       //skip multiple registrations
diff --git a/platform/lang-impl/src/com/intellij/openapi/roots/ui/configuration/SdkListItem.java b/platform/lang-impl/src/com/intellij/openapi/roots/ui/configuration/SdkListItem.java
index 0abe217aea6a..46487eef4bf1 100644
--- a/platform/lang-impl/src/com/intellij/openapi/roots/ui/configuration/SdkListItem.java
+++ b/platform/lang-impl/src/com/intellij/openapi/roots/ui/configuration/SdkListItem.java
@@ -121,14 +121,14 @@ public abstract class SdkListItem {
     }
   }
 
-  enum ActionRole {
+  public enum ActionRole {
     DOWNLOAD, ADD
   }
 
   public static final class ActionItem extends SdkListItem {
     @Nullable final GroupItem myGroup;
     @NotNull final ActionRole myRole;
-    @NotNull  final NewSdkAction myAction;
+    @NotNull final NewSdkAction myAction;
 
     ActionItem(@NotNull ActionRole role, @NotNull NewSdkAction action, @Nullable GroupItem group) {
       myRole = role;
@@ -136,6 +136,16 @@ public abstract class SdkListItem {
       myGroup = group;
     }
 
+    @NotNull
+    public ActionRole getRole() {
+      return myRole;
+    }
+
+    @NotNull
+    public NewSdkAction getAction() {
+      return myAction;
+    }
+
     @NotNull
     ActionItem withGroup(@NotNull GroupItem group) {
       return new ActionItem(myRole, myAction, group);
diff --git a/platform/lang-impl/testSources/com/intellij/openapi/roots/ui/configuration/SdkComboBoxTest.kt b/platform/lang-impl/testSources/com/intellij/openapi/roots/ui/configuration/SdkComboBoxTest.kt
new file mode 100644
index 000000000000..e1981fec490c
--- /dev/null
+++ b/platform/lang-impl/testSources/com/intellij/openapi/roots/ui/configuration/SdkComboBoxTest.kt
@@ -0,0 +1,116 @@
+// Copyright 2000-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package com.intellij.openapi.roots.ui.configuration
+
+import com.intellij.openapi.projectRoots.ProjectJdkTable
+import com.intellij.openapi.projectRoots.Sdk
+
+class SdkComboBoxTest : SdkComboBoxTestCase() {
+
+  fun `test simple usage`() {
+    val sdk1 = createAndRegisterSdk()
+    val sdk2 = createAndRegisterSdk(isProjectSdk = true)
+    val sdk3 = createAndRegisterSdk()
+    val sdk4 = TestSdkGenerator.createNextSdk()
+    val comboBox = createComboBox()
+
+    assertComboBoxContent(comboBox)
+      .item<SdkListItem.ProjectSdkItem> { assertEquals(sdk2, comboBox.getProjectSdk()) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(sdk1, it) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(sdk2, it) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(sdk3, it) }
+      .nothing()
+
+    assertComboBoxSelection<SdkListItem.NoneSdkItem>(comboBox, null)
+    comboBox.setSelectedSdk(sdk1)
+    assertComboBoxSelection<SdkListItem.SdkItem>(comboBox, sdk1)
+    comboBox.setSelectedSdk(sdk2)
+    assertComboBoxSelection<SdkListItem.SdkItem>(comboBox, sdk2)
+    comboBox.setSelectedSdk(sdk3)
+    assertComboBoxSelection<SdkListItem.SdkItem>(comboBox, sdk3)
+    comboBox.setSelectedSdk(sdk4)
+    assertComboBoxSelection<SdkListItem.InvalidSdkItem>(comboBox, null)
+    comboBox.setSelectedSdk(null)
+    assertComboBoxSelection<SdkListItem.NoneSdkItem>(comboBox, null)
+
+    assertComboBoxContent(comboBox)
+      .item<SdkListItem.NoneSdkItem>(isSelected = true)
+      .item<SdkListItem.ProjectSdkItem> { assertEquals(sdk2, comboBox.getProjectSdk()) }
+      .item<SdkListItem.InvalidSdkItem> { assertEquals(sdk4.name, it.sdkName) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(sdk1, it) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(sdk2, it) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(sdk3, it) }
+      .nothing()
+
+    comboBox.setSelectedItem(SdkListItem.ProjectSdkItem())
+    assertComboBoxSelection<SdkListItem.ProjectSdkItem>(comboBox, sdk2)
+    comboBox.setSelectedItem(SdkListItem.NoneSdkItem())
+    assertComboBoxSelection<SdkListItem.NoneSdkItem>(comboBox, null)
+    comboBox.setSelectedItem(SdkListItem.InvalidSdkItem("invalid sdk"))
+    assertComboBoxSelection<SdkListItem.InvalidSdkItem>(comboBox, null)
+
+    assertComboBoxContent(comboBox)
+      .item<SdkListItem.NoneSdkItem>()
+      .item<SdkListItem.ProjectSdkItem> { assertEquals(sdk2, comboBox.getProjectSdk()) }
+      .item<SdkListItem.InvalidSdkItem>(isSelected = true) { assertEquals("invalid sdk", it.sdkName) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(sdk1, it) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(sdk2, it) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(sdk3, it) }
+      .nothing()
+  }
+
+  fun `test combobox actions`() {
+    val comboBox = createComboBox()
+      .withOpenDropdownPopup()
+
+    assertComboBoxContent(comboBox)
+      .item<SdkListItem.ActionItem> { assertActionItem(SdkListItem.ActionRole.DOWNLOAD, it) }
+      .item<SdkListItem.ActionItem> { assertActionItem(SdkListItem.ActionRole.ADD, it) }
+      .nothing()
+
+    val download1 = comboBox.touchDownloadAction()
+    val download2 = comboBox.touchDownloadAction()
+    val download3 = comboBox.touchDownloadAction()
+    val download4 = comboBox.touchDownloadAction()
+
+    assertComboBoxContent(comboBox)
+      .item<SdkListItem.SdkItem> { assertSdkItem(download1, it) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(download2, it) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(download3, it) }
+      .item<SdkListItem.SdkItem>(isSelected = true) { assertSdkItem(download4, it) }
+      .item<SdkListItem.ActionItem> { assertActionItem(SdkListItem.ActionRole.DOWNLOAD, it) }
+      .item<SdkListItem.ActionItem> { assertActionItem(SdkListItem.ActionRole.ADD, it) }
+      .nothing()
+
+    val add1 = comboBox.touchAddAction()
+    val add2 = comboBox.touchAddAction()
+    val add3 = comboBox.touchAddAction()
+    val add4 = comboBox.touchAddAction()
+
+    assertComboBoxContent(comboBox)
+      .item<SdkListItem.SdkItem> { assertSdkItem(download1, it) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(download2, it) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(download3, it) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(download4, it) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(add1, it) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(add2, it) }
+      .item<SdkListItem.SdkItem> { assertSdkItem(add3, it) }
+      .item<SdkListItem.SdkItem>(isSelected = true) { assertSdkItem(add4, it) }
+      .item<SdkListItem.ActionItem> { assertActionItem(SdkListItem.ActionRole.DOWNLOAD, it) }
+      .item<SdkListItem.ActionItem> { assertActionItem(SdkListItem.ActionRole.ADD, it) }
+      .nothing()
+
+    assertCollectionContent(comboBox.model.sdksModel.projectSdks.values.sortedBy { it.name })
+      .element<Sdk> { assertSdk(download1, it) }
+      .element<Sdk> { assertSdk(download2, it) }
+      .element<Sdk> { assertSdk(download3, it) }
+      .element<Sdk> { assertSdk(download4, it) }
+      .element<Sdk> { assertSdk(add1, it) }
+      .element<Sdk> { assertSdk(add2, it) }
+      .element<Sdk> { assertSdk(add3, it) }
+      .element<Sdk> { assertSdk(add4, it) }
+      .nothing()
+
+    assertCollectionContent(ProjectJdkTable.getInstance().getSdksOfType(TestSdkType))
+      .nothing()
+  }
+}
\ No newline at end of file
diff --git a/platform/lang-impl/testSources/com/intellij/openapi/roots/ui/configuration/SdkComboBoxTestCase.kt b/platform/lang-impl/testSources/com/intellij/openapi/roots/ui/configuration/SdkComboBoxTestCase.kt
new file mode 100644
index 000000000000..5f3c7a276c71
--- /dev/null
+++ b/platform/lang-impl/testSources/com/intellij/openapi/roots/ui/configuration/SdkComboBoxTestCase.kt
@@ -0,0 +1,208 @@
+// Copyright 2000-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package com.intellij.openapi.roots.ui.configuration
+
+import com.intellij.openapi.Disposable
+import com.intellij.openapi.application.invokeAndWaitIfNeeded
+import com.intellij.openapi.application.runWriteAction
+import com.intellij.openapi.project.Project
+import com.intellij.openapi.projectRoots.ProjectJdkTable
+import com.intellij.openapi.projectRoots.Sdk
+import com.intellij.openapi.projectRoots.SdkType
+import com.intellij.openapi.projectRoots.SdkTypeId
+import com.intellij.openapi.roots.ui.configuration.SdkComboBoxModel.Companion.createSdkComboBoxModel
+import com.intellij.openapi.roots.ui.configuration.projectRoot.ProjectSdksModel
+import com.intellij.openapi.util.Disposer
+import java.util.function.Predicate
+
+abstract class SdkComboBoxTestCase : SdkTestCase() {
+
+  fun createComboBox(filter: (SdkTypeId) -> Boolean = { true }): SdkComboBox {
+    val sdksModel = TestProjectSdksModel()
+    sdksModel.reset(project)
+    Disposer.register(project, sdksModel)
+    val model = createSdkComboBoxModel(project, sdksModel, Predicate { TestSdkType == it || filter(it) })
+    return SdkComboBox(model)
+  }
+
+  class ComboBoxChecker(val comboBox: SdkComboBox) :
+    CollectionChecker<SdkListItem>(comboBox.itemSequence.iterator(), comboBox.dumpToString()) {
+
+    inline fun <reified I : SdkListItem> item(
+      isSelected: Boolean = false,
+      noinline assertItem: SdkComboBox.(I) -> Unit = {}
+    ): ComboBoxChecker {
+      element<I> {
+        assertSelection(comboBox, it, isSelected)
+        comboBox.assertItem(it)
+      }
+      return this
+    }
+
+    fun assertSelection(comboBox: SdkComboBox, elementToCheck: SdkListItem, mustBeSelected: Boolean) {
+      if (mustBeSelected) {
+        val message = "'${comboBox.dumpToString(elementToCheck)}' must be selected"
+        assertTrue(message, comboBox.selectedItem == elementToCheck)
+      }
+      else {
+        val message = "'${comboBox.dumpToString(elementToCheck)}' must not be selected"
+        assertFalse(message, comboBox.selectedItem == elementToCheck)
+      }
+    }
+  }
+
+  open class CollectionChecker<T : Any>(val iterator: Iterator<T?>, val dump: String) {
+
+    inline fun <reified I : T> element(noinline assertItem: (I) -> Unit = {}): CollectionChecker<T> {
+      assertTrue(dump, iterator.hasNext())
+      val element = iterator.next()
+      val item = assertIsInstance<I>(dump, element)
+      withMessageIfException { assertItem(item) }
+      return this
+    }
+
+    fun nothing() {
+      assertFalse(dump, iterator.hasNext())
+    }
+
+    fun <R> withMessageIfException(action: () -> R): R {
+      try {
+        return action()
+      }
+      catch (ex: Throwable) {
+        System.err.println("${ex::class.java.name}: $dump")
+        throw ex
+      }
+    }
+  }
+
+  /**
+   * Works in team with:
+   *  [SdkConfigurationUtil.selectSdkHome(SdkType, Component, Consumer<in String>)],
+   *  [SdkComboBoxTestCase.TestProjectSdksModel]
+   */
+  object CanarySdk : TestSdk("canary", "canary-home", "canary-version") {
+    fun <R> replaceByTestSdk(action: () -> R): R {
+      return invokeAndWaitIfNeeded {
+        runWriteAction {
+          val projectSdkTable = ProjectJdkTable.getInstance()
+          projectSdkTable.addJdk(CanarySdk)
+          try {
+            action()
+          }
+          finally {
+            projectSdkTable.removeJdk(CanarySdk)
+          }
+        }
+      }
+    }
+  }
+
+  class TestProjectSdksModel : ProjectSdksModel(), Disposable {
+    override fun addSdk(type: SdkType, home: String, callback: com.intellij.util.Consumer<in Sdk>?) {
+      if (home == CanarySdk.homePath) {
+        val sdk = TestSdkGenerator.createNextSdk()
+        setupSdk(sdk, callback)
+      }
+      else {
+        super.addSdk(type, home, callback)
+      }
+    }
+
+    private fun setupSdk(newJdk: TestSdk, callback: com.intellij.util.Consumer<in Sdk>?) {
+      val sdkType = newJdk.sdkType as SdkType
+      if (!sdkType.setupSdkPaths(newJdk, this)) return
+      doAdd(newJdk, callback)
+    }
+
+    override fun reset(project: Project?) {
+      disposeEditableSdks()
+      super.reset(project)
+    }
+
+    override fun dispose() = disposeEditableSdks()
+
+    private fun disposeEditableSdks() {
+      for (editable in projectSdks.values) {
+        if (editable is Disposable) {
+          Disposer.dispose(editable)
+        }
+      }
+    }
+  }
+
+  companion object {
+    fun assertSdkItem(expected: Sdk, item: SdkListItem.SdkItem) {
+      assertSdk(expected, item.sdk)
+    }
+
+    fun assertActionItem(role: SdkListItem.ActionRole, item: SdkListItem.ActionItem) {
+      assertEquals(role, item.role)
+      assertEquals(TestSdkType, item.action.sdkType)
+    }
+
+    inline fun <reified I : SdkListItem> assertComboBoxSelection(comboBox: SdkComboBox, expectedSdk: Sdk?) {
+      assertEquals(comboBox.dumpToString(), expectedSdk, comboBox.getSelectedSdk())
+      assertIsInstance<I>(comboBox.dumpToString(), comboBox.getSelectedItem())
+    }
+
+    fun assertComboBoxContent(comboBox: SdkComboBox) = ComboBoxChecker(comboBox)
+
+    fun assertCollectionContent(collection: Collection<*>) = CollectionChecker(collection.iterator(), collection.toString())
+
+    inline fun <reified T> assertIsInstance(message: String, o: Any?): T {
+      requireNotNull(o) { message }
+      assertTrue("Expected instance of: ${T::class.java.name} actual: ${o::class.java.name}, $message", o is T)
+      return o as T
+    }
+
+    fun SdkComboBox.getProjectSdk() = model.sdksModel.projectSdk?.let { TestSdkGenerator.findTestSdk(it) }
+
+    val SdkComboBox.itemSequence
+      get() = sequence {
+        val model = getModel()
+        for (i in 0 until model.getSize()) {
+          yield(model.getElementAt(i))
+        }
+      }
+
+    fun SdkComboBox.touchDownloadAction(): TestSdk {
+      selectedItem = itemSequence
+        .filterIsInstance<SdkListItem.ActionItem>()
+        .first { it.role == SdkListItem.ActionRole.DOWNLOAD }
+      return TestSdkGenerator.getCurrentSdk()
+    }
+
+    fun SdkComboBox.touchAddAction(): TestSdk {
+      CanarySdk.replaceByTestSdk {
+        selectedItem = itemSequence
+          .filterIsInstance<SdkListItem.ActionItem>()
+          .first { it.role == SdkListItem.ActionRole.ADD }
+      }
+      return TestSdkGenerator.getCurrentSdk()
+    }
+
+    fun SdkComboBox.withOpenDropdownPopup(): SdkComboBox {
+      firePopupMenuWillBecomeVisible()
+      return this
+    }
+
+    fun SdkComboBox.dumpToString(): String {
+      val elements = itemSequence.joinToString { (if (selectedItem == it) "* " else "") + dumpToString(it) }
+      return "ComboBox { $elements }"
+    }
+
+    fun SdkComboBox.dumpToString(element: SdkListItem?): String {
+      return when (element) {
+        is SdkListItem.NoneSdkItem -> "[none]"
+        is SdkListItem.ProjectSdkItem -> "[project] ${getProjectSdk()?.name}"
+        is SdkListItem.InvalidSdkItem -> "[invalid] ${element.sdkName}"
+        is SdkListItem.SdkItem -> "[sdk] ${element.sdk.name}"
+        is SdkListItem.SuggestedItem -> "[suggested] ${element.homePath}"
+        is SdkListItem.ActionItem -> "[action] ${element.myRole} ${element.myAction.sdkType.name}"
+        is SdkListItem.GroupItem -> "[group] {${element.mySubItems.joinToString { dumpToString(it) }}}"
+        null -> "null"
+        else -> element::class.java.name
+      }
+    }
+  }
+}
\ No newline at end of file
diff --git a/platform/lang-impl/testSources/com/intellij/openapi/roots/ui/configuration/SdkTestCase.kt b/platform/lang-impl/testSources/com/intellij/openapi/roots/ui/configuration/SdkTestCase.kt
new file mode 100644
index 000000000000..65c87dca3a95
--- /dev/null
+++ b/platform/lang-impl/testSources/com/intellij/openapi/roots/ui/configuration/SdkTestCase.kt
@@ -0,0 +1,154 @@
+// Copyright 2000-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package com.intellij.openapi.roots.ui.configuration
+
+import com.intellij.openapi.application.invokeAndWaitIfNeeded
+import com.intellij.openapi.application.runWriteAction
+import com.intellij.openapi.progress.ProgressIndicator
+import com.intellij.openapi.projectRoots.*
+import com.intellij.openapi.projectRoots.impl.MockSdk
+import com.intellij.openapi.roots.ProjectRootManager
+import com.intellij.openapi.roots.ui.configuration.projectRoot.SdkDownload
+import com.intellij.openapi.roots.ui.configuration.projectRoot.SdkDownloadTask
+import com.intellij.openapi.util.Disposer
+import com.intellij.openapi.util.io.FileUtil
+import com.intellij.testFramework.LightPlatformTestCase
+import com.intellij.util.containers.MultiMap
+import org.jdom.Element
+import java.io.File
+import java.util.*
+import java.util.function.Consumer
+import javax.swing.JComponent
+import kotlin.collections.LinkedHashMap
+
+abstract class SdkTestCase : LightPlatformTestCase() {
+
+  override fun setUp() {
+    super.setUp()
+
+    TestSdkGenerator.reset()
+    SdkType.EP_NAME.getPoint(null)
+      .registerExtension(TestSdkType, project)
+    SdkDownload.EP_NAME.getPoint(null)
+      .registerExtension(TestSdkDownloader, project)
+  }
+
+  override fun tearDown() {
+    Disposer.disposeChildren(project)
+    closeAndDeleteProject()
+
+    super.tearDown()
+  }
+
+  fun createAndRegisterSdk(isProjectSdk: Boolean = false): Sdk {
+    val sdk = TestSdkGenerator.createNextSdk()
+    registerSdk(sdk)
+    if (isProjectSdk) {
+      setProjectSdk(sdk)
+    }
+    return sdk
+  }
+
+  private fun registerSdk(sdk: Sdk) {
+    invokeAndWaitIfNeeded {
+      runWriteAction {
+        val jdkTable = ProjectJdkTable.getInstance()
+        jdkTable.addJdk(sdk, project)
+      }
+    }
+  }
+
+  private fun setProjectSdk(sdk: Sdk) {
+    invokeAndWaitIfNeeded {
+      runWriteAction {
+        val rootManager = ProjectRootManager.getInstance(project)
+        rootManager.projectSdk = sdk
+      }
+    }
+  }
+
+  object TestSdkType : SdkType("test-type"), JavaSdkType {
+    override fun getPresentableName(): String = name
+    override fun isValidSdkHome(path: String?): Boolean = true
+    override fun suggestSdkName(currentSdkName: String?, sdkHome: String?): String = "sdk-name"
+    override fun suggestHomePath(): String? = null
+    override fun createAdditionalDataConfigurable(sdkModel: SdkModel, sdkModificator: SdkModificator): AdditionalDataConfigurable? = null
+    override fun saveAdditionalData(additionalData: SdkAdditionalData, additional: Element) {}
+    override fun getBinPath(sdk: Sdk): String = File(sdk.homePath, "bin").path
+    override fun getToolsPath(sdk: Sdk): String = File(sdk.homePath, "lib/tools.jar").path
+    override fun getVMExecutablePath(sdk: Sdk): String = File(sdk.homePath, "bin/java").path
+  }
+
+  open class TestSdk(name: String, homePath: String, versionString: String)
+    : MockSdk(name, homePath, versionString, MultiMap(), TestSdkType) {
+    override fun getHomePath(): String = super.getHomePath()!!
+  }
+
+  object TestSdkDownloader : SdkDownload {
+    override fun supportsDownload(sdkTypeId: SdkTypeId) = sdkTypeId == TestSdkType
+
+    override fun showDownloadUI(
+      sdkTypeId: SdkTypeId,
+      sdkModel: SdkModel,
+      parentComponent: JComponent,
+      selectedSdk: Sdk?,
+      sdkCreatedCallback: Consumer<SdkDownloadTask>
+    ) {
+      val sdk = TestSdkGenerator.createNextSdk()
+      sdkCreatedCallback.accept(object : SdkDownloadTask {
+        override fun doDownload(indicator: ProgressIndicator) {}
+        override fun getPlannedVersion() = sdk.versionString
+        override fun getSuggestedSdkName() = sdk.name
+        override fun getPlannedHomeDir() = sdk.homePath
+      })
+    }
+  }
+
+  object TestSdkGenerator {
+    private var createdSdkCounter = 0
+    private lateinit var createdSdks: MutableMap<String, TestSdk>
+
+    fun findTestSdk(sdk: Sdk): TestSdk? = createdSdks[sdk.name]
+
+    fun getCurrentSdk() = createdSdks.values.last()
+
+    fun createNextSdk(): TestSdk {
+      val name = "test-name (${createdSdkCounter++})"
+      val versionString = "11"
+      val homePath = FileUtil.getTempDirectory() + "/jdk-$name"
+      generateJdkStructure(homePath, versionString)
+      createdSdks[name] = TestSdk(name, homePath, versionString)
+      return getCurrentSdk()
+    }
+
+    private fun generateJdkStructure(homePath: String, versionString: String) {
+      createFile("$homePath/release")
+      createFile("$homePath/jre/lib/rt.jar")
+      createFile("$homePath/bin/javac")
+      createFile("$homePath/bin/java")
+      val properties = Properties()
+      properties.setProperty("JAVA_FULL_VERSION", versionString)
+      File("$homePath/release").outputStream().use {
+        properties.store(it, null)
+      }
+    }
+
+    private fun createFile(path: String) {
+      val file = File(path)
+      file.parentFile.mkdirs()
+      file.createNewFile()
+    }
+
+    fun reset() {
+      createdSdkCounter = 0
+      createdSdks = LinkedHashMap()
+    }
+  }
+
+  companion object {
+    fun assertSdk(expected: Sdk, actual: Sdk) {
+      assertEquals(expected.name, actual.name)
+      assertEquals(expected.sdkType, actual.sdkType)
+      assertEquals(expected, TestSdkGenerator.findTestSdk(actual))
+    }
+  }
+}
\ No newline at end of file