gopls/internal/regtest: move TestMultipleModules_Warning to ./workspace

This test is really about workspace setup, not diagnostics. Move it
in advance of changes to this feature.

Pure code move, no other changes.

Change-Id: Ib78f1fe5ce701673f5aa071f399da11f208874df
Reviewed-on: https://go-review.googlesource.com/c/tools/+/421498
Reviewed-by: Suzy Mueller <suzmue@golang.org>

gopls/internal/regtest/diagnostics/diagnostics_test.go

@@ -1692,57 +1692,6 @@ import (
 	})
 }
 
-func TestMultipleModules_Warning(t *testing.T) {
-	const modules = `
--- a/go.mod --
-module a.com
-
-go 1.12
--- a/a.go --
-package a
--- b/go.mod --
-module b.com
-
-go 1.12
--- b/b.go --
-package b
-`
-	for _, go111module := range []string{"on", "auto"} {
-		t.Run("GO111MODULE="+go111module, func(t *testing.T) {
-			WithOptions(
-				Modes(Default),
-				EnvVars{"GO111MODULE": go111module},
-			).Run(t, modules, func(t *testing.T, env *Env) {
-				env.OpenFile("a/a.go")
-				env.OpenFile("b/go.mod")
-				env.Await(
-					env.DiagnosticAtRegexp("a/a.go", "package a"),
-					env.DiagnosticAtRegexp("b/go.mod", "module b.com"),
-					OutstandingWork(lsp.WorkspaceLoadFailure, "gopls requires a module at the root of your workspace."),
-				)
-			})
-		})
-	}
-
-	// Expect no warning if GO111MODULE=auto in a directory in GOPATH.
-	t.Run("GOPATH_GO111MODULE_auto", func(t *testing.T) {
-		WithOptions(
-			Modes(Default),
-			EnvVars{"GO111MODULE": "auto"},
-			InGOPATH(),
-		).Run(t, modules, func(t *testing.T, env *Env) {
-			env.OpenFile("a/a.go")
-			env.Await(
-				OnceMet(
-					env.DoneWithOpen(),
-					EmptyDiagnostics("a/a.go"),
-				),
-				NoOutstandingWork(),
-			)
-		})
-	})
-}
-
 func TestNestedModules(t *testing.T) {
 	const proxy = `
 -- nested.com@v1.0.0/go.mod --

gopls/internal/regtest/workspace/broken_test.go

@@ -167,3 +167,54 @@ const F = named.D - 3
 		env.Await(NoOutstandingDiagnostics())
 	})
 }
+
+func TestMultipleModules_Warning(t *testing.T) {
+	const modules = `
+-- a/go.mod --
+module a.com
+
+go 1.12
+-- a/a.go --
+package a
+-- b/go.mod --
+module b.com
+
+go 1.12
+-- b/b.go --
+package b
+`
+	for _, go111module := range []string{"on", "auto"} {
+		t.Run("GO111MODULE="+go111module, func(t *testing.T) {
+			WithOptions(
+				Modes(Default),
+				EnvVars{"GO111MODULE": go111module},
+			).Run(t, modules, func(t *testing.T, env *Env) {
+				env.OpenFile("a/a.go")
+				env.OpenFile("b/go.mod")
+				env.Await(
+					env.DiagnosticAtRegexp("a/a.go", "package a"),
+					env.DiagnosticAtRegexp("b/go.mod", "module b.com"),
+					OutstandingWork(lsp.WorkspaceLoadFailure, "gopls requires a module at the root of your workspace."),
+				)
+			})
+		})
+	}
+
+	// Expect no warning if GO111MODULE=auto in a directory in GOPATH.
+	t.Run("GOPATH_GO111MODULE_auto", func(t *testing.T) {
+		WithOptions(
+			Modes(Default),
+			EnvVars{"GO111MODULE": "auto"},
+			InGOPATH(),
+		).Run(t, modules, func(t *testing.T, env *Env) {
+			env.OpenFile("a/a.go")
+			env.Await(
+				OnceMet(
+					env.DoneWithOpen(),
+					EmptyDiagnostics("a/a.go"),
+				),
+				NoOutstandingWork(),
+			)
+		})
+	})
+}