Add first multi-workspace IDE test

Author: Duhemm

language-server/test/dotty/tools/languageserver/DefinitionTest.scala

@@ -19,6 +19,20 @@ class DefinitionTest {
       .definition(m5 to m6, List(m1 to m2))
   }
 
+  @Test def classDefinitionDifferentWorkspace: Unit = {
+    val w0 = Workspace.withSources(
+      code"""class ${m1}Foo${m2}"""
+    )
+
+    val w1 = Workspace.dependingOn(w0).withSources(
+      code"""class Bar { new ${m3}Foo${m4} }"""
+    )
+
+    withWorkspaces(w0, w1)
+      .definition(m1 to m2, List(m1 to m2))
+      .definition(m3 to m4, List(m1 to m2))
+  }
+
   @Test def valDefinition0: Unit = {
     withSources(
       code"class Foo { val ${m1}x$m2 = 0; ${m3}x$m4 }",