diff --git a/go/packages/golist_fallback.go b/go/packages/golist_fallback.go
index 6b8d537a..ea484706 100644
--- a/go/packages/golist_fallback.go
+++ b/go/packages/golist_fallback.go
@@ -67,17 +67,32 @@ func golistDriverFallback(cfg *Config, words ...string) (*driverResponse, error)
 		compiledGoFiles := absJoin(p.Dir, p.GoFiles)
 		// Use a function to simplify control flow. It's just a bunch of gotos.
 		var cgoErrors []error
+		var outdir string
+		getOutdir := func() (string, error) {
+			if outdir != "" {
+				return outdir, nil
+			}
+			if tmpdir == "" {
+				if tmpdir, err = ioutil.TempDir("", "gopackages"); err != nil {
+					return "", err
+				}
+			}
+			// Add a "go-build" component to the path to make the tests think the files are in the cache.
+			// This allows the same test to test the pre- and post-Go 1.11 go list logic because the Go 1.11
+			// go list generates test mains in the cache, and the test code knows not to rely on paths in the
+			// cache to stay stable.
+			outdir = filepath.Join(tmpdir, "go-build", strings.Replace(p.ImportPath, "/", "_", -1))
+			if err := os.MkdirAll(outdir, 0755); err != nil {
+				outdir = ""
+				return "", err
+			}
+			return outdir, nil
+		}
 		processCgo := func() bool {
 			// Suppress any cgo errors. Any relevant errors will show up in typechecking.
 			// TODO(matloob): Skip running cgo if Mode < LoadTypes.
-			if tmpdir == "" {
-				if tmpdir, err = ioutil.TempDir("", "gopackages"); err != nil {
-					cgoErrors = append(cgoErrors, err)
-					return false
-				}
-			}
-			outdir := filepath.Join(tmpdir, strings.Replace(p.ImportPath, "/", "_", -1))
-			if err := os.Mkdir(outdir, 0755); err != nil {
+			outdir, err := getOutdir()
+			if err != nil {
 				cgoErrors = append(cgoErrors, err)
 				return false
 			}
@@ -111,7 +126,7 @@ func golistDriverFallback(cfg *Config, words ...string) (*driverResponse, error)
 				if isRoot {
 					response.Roots = append(response.Roots, testID)
 				}
-				response.Packages = append(response.Packages, &Package{
+				testPkg := &Package{
 					ID:              testID,
 					Name:            p.Name,
 					GoFiles:         absJoin(p.Dir, p.GoFiles, p.CgoFiles, p.TestGoFiles),
@@ -120,7 +135,9 @@ func golistDriverFallback(cfg *Config, words ...string) (*driverResponse, error)
 					PkgPath:         pkgpath,
 					Imports:         importMap(append(p.Imports, p.TestImports...)),
 					// TODO(matloob): set errors on the Package to cgoErrors
-				})
+				}
+				response.Packages = append(response.Packages, testPkg)
+				var xtestPkg *Package
 				if len(p.XTestGoFiles) > 0 {
 					xtestID := fmt.Sprintf("%s_test [%s.test]", id, id)
 					if isRoot {
@@ -134,15 +151,51 @@ func golistDriverFallback(cfg *Config, words ...string) (*driverResponse, error)
 							break
 						}
 					}
-					response.Packages = append(response.Packages, &Package{
+					xtestPkg = &Package{
 						ID:              xtestID,
 						Name:            p.Name + "_test",
 						GoFiles:         absJoin(p.Dir, p.XTestGoFiles),
 						CompiledGoFiles: absJoin(p.Dir, p.XTestGoFiles),
-						PkgPath:         pkgpath,
+						PkgPath:         pkgpath + "_test",
 						Imports:         imports,
-					})
+					}
+					response.Packages = append(response.Packages, xtestPkg)
 				}
+				// testmain package
+				testmainID := id + ".test"
+				if isRoot {
+					response.Roots = append(response.Roots, testmainID)
+				}
+				imports := map[string]*Package{}
+				imports[testPkg.PkgPath] = &Package{ID: testPkg.ID}
+				if xtestPkg != nil {
+					imports[xtestPkg.PkgPath] = &Package{ID: xtestPkg.ID}
+				}
+				testmainPkg := &Package{
+					ID:      testmainID,
+					Name:    "main",
+					PkgPath: testmainID,
+					Imports: imports,
+				}
+				response.Packages = append(response.Packages, testmainPkg)
+				outdir, err := getOutdir()
+				if err != nil {
+					testmainPkg.Errors = append(testmainPkg.Errors,
+						Error{"-", fmt.Sprintf("failed to generate testmain: %v", err)})
+					return
+				}
+				testmain := filepath.Join(outdir, "testmain.go")
+				extradeps, err := generateTestmain(testmain, testPkg, xtestPkg)
+				if err != nil {
+					testmainPkg.Errors = append(testmainPkg.Errors,
+						Error{"-", fmt.Sprintf("failed to generate testmain: %v", err)})
+				}
+				deps = append(deps, extradeps...)
+				for _, imp := range extradeps { // testing, testing/internal/testdeps, and maybe os
+					imports[imp] = &Package{ID: imp}
+				}
+				testmainPkg.GoFiles = []string{testmain}
+				testmainPkg.CompiledGoFiles = []string{testmain}
 			}
 		}
 	}
@@ -169,6 +222,11 @@ func golistDriverFallback(cfg *Config, words ...string) (*driverResponse, error)
 		addPackage(p)
 	}
 
+	// TODO(matloob): Is this the right ordering?
+	sort.SliceStable(response.Packages, func(i, j int) bool {
+		return response.Packages[i].PkgPath < response.Packages[j].PkgPath
+	})
+
 	return &response, nil
 }
 
diff --git a/go/packages/golist_fallback_testmain.go b/go/packages/golist_fallback_testmain.go
new file mode 100644
index 00000000..37541707
--- /dev/null
+++ b/go/packages/golist_fallback_testmain.go
@@ -0,0 +1,268 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file is largely based on the Go 1.10-era cmd/go/internal/test/test.go
+// testmain generation code.
+
+package packages
+
+import (
+	"errors"
+	"fmt"
+	"go/ast"
+	"go/doc"
+	"go/parser"
+	"go/token"
+	"os"
+	"sort"
+	"strings"
+	"text/template"
+	"unicode"
+	"unicode/utf8"
+)
+
+// TODO(matloob): Delete this file once Go 1.12 is released.
+
+// This file complements golist_fallback.go by providing
+// support for generating testmains.
+
+func generateTestmain(out string, testPkg, xtestPkg *Package) (extradeps []string, err error) {
+	testFuncs, err := loadTestFuncs(testPkg, xtestPkg)
+	if err != nil {
+		return nil, err
+	}
+	extradeps = []string{"testing/internal/testdeps", "testing"}
+	if testFuncs.TestMain == nil {
+		extradeps = append(extradeps, "os")
+	}
+	return extradeps, writeTestmain(out, testFuncs)
+}
+
+// The following is adapted from the cmd/go testmain generation code.
+
+// isTestFunc tells whether fn has the type of a testing function. arg
+// specifies the parameter type we look for: B, M or T.
+func isTestFunc(fn *ast.FuncDecl, arg string) bool {
+	if fn.Type.Results != nil && len(fn.Type.Results.List) > 0 ||
+		fn.Type.Params.List == nil ||
+		len(fn.Type.Params.List) != 1 ||
+		len(fn.Type.Params.List[0].Names) > 1 {
+		return false
+	}
+	ptr, ok := fn.Type.Params.List[0].Type.(*ast.StarExpr)
+	if !ok {
+		return false
+	}
+	// We can't easily check that the type is *testing.M
+	// because we don't know how testing has been imported,
+	// but at least check that it's *M or *something.M.
+	// Same applies for B and T.
+	if name, ok := ptr.X.(*ast.Ident); ok && name.Name == arg {
+		return true
+	}
+	if sel, ok := ptr.X.(*ast.SelectorExpr); ok && sel.Sel.Name == arg {
+		return true
+	}
+	return false
+}
+
+// isTest tells whether name looks like a test (or benchmark, according to prefix).
+// It is a Test (say) if there is a character after Test that is not a lower-case letter.
+// We don't want TesticularCancer.
+func isTest(name, prefix string) bool {
+	if !strings.HasPrefix(name, prefix) {
+		return false
+	}
+	if len(name) == len(prefix) { // "Test" is ok
+		return true
+	}
+	rune, _ := utf8.DecodeRuneInString(name[len(prefix):])
+	return !unicode.IsLower(rune)
+}
+
+// loadTestFuncs returns the testFuncs describing the tests that will be run.
+func loadTestFuncs(ptest, pxtest *Package) (*testFuncs, error) {
+	t := &testFuncs{
+		TestPackage:  ptest,
+		XTestPackage: pxtest,
+	}
+	for _, file := range ptest.GoFiles {
+		if !strings.HasSuffix(file, "_test.go") {
+			continue
+		}
+		if err := t.load(file, "_test", &t.ImportTest, &t.NeedTest); err != nil {
+			return nil, err
+		}
+	}
+	if pxtest != nil {
+		for _, file := range pxtest.GoFiles {
+			if err := t.load(file, "_xtest", &t.ImportXtest, &t.NeedXtest); err != nil {
+				return nil, err
+			}
+		}
+	}
+	return t, nil
+}
+
+// writeTestmain writes the _testmain.go file for t to the file named out.
+func writeTestmain(out string, t *testFuncs) error {
+	f, err := os.Create(out)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	if err := testmainTmpl.Execute(f, t); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+type testFuncs struct {
+	Tests        []testFunc
+	Benchmarks   []testFunc
+	Examples     []testFunc
+	TestMain     *testFunc
+	TestPackage  *Package
+	XTestPackage *Package
+	ImportTest   bool
+	NeedTest     bool
+	ImportXtest  bool
+	NeedXtest    bool
+}
+
+// Tested returns the name of the package being tested.
+func (t *testFuncs) Tested() string {
+	return t.TestPackage.Name
+}
+
+type testFunc struct {
+	Package   string // imported package name (_test or _xtest)
+	Name      string // function name
+	Output    string // output, for examples
+	Unordered bool   // output is allowed to be unordered.
+}
+
+func (t *testFuncs) load(filename, pkg string, doImport, seen *bool) error {
+	var fset = token.NewFileSet()
+
+	f, err := parser.ParseFile(fset, filename, nil, parser.ParseComments)
+	if err != nil {
+		return errors.New("failed to parse test file " + filename)
+	}
+	for _, d := range f.Decls {
+		n, ok := d.(*ast.FuncDecl)
+		if !ok {
+			continue
+		}
+		if n.Recv != nil {
+			continue
+		}
+		name := n.Name.String()
+		switch {
+		case name == "TestMain":
+			if isTestFunc(n, "T") {
+				t.Tests = append(t.Tests, testFunc{pkg, name, "", false})
+				*doImport, *seen = true, true
+				continue
+			}
+			err := checkTestFunc(fset, n, "M")
+			if err != nil {
+				return err
+			}
+			if t.TestMain != nil {
+				return errors.New("multiple definitions of TestMain")
+			}
+			t.TestMain = &testFunc{pkg, name, "", false}
+			*doImport, *seen = true, true
+		case isTest(name, "Test"):
+			err := checkTestFunc(fset, n, "T")
+			if err != nil {
+				return err
+			}
+			t.Tests = append(t.Tests, testFunc{pkg, name, "", false})
+			*doImport, *seen = true, true
+		case isTest(name, "Benchmark"):
+			err := checkTestFunc(fset, n, "B")
+			if err != nil {
+				return err
+			}
+			t.Benchmarks = append(t.Benchmarks, testFunc{pkg, name, "", false})
+			*doImport, *seen = true, true
+		}
+	}
+	ex := doc.Examples(f)
+	sort.Slice(ex, func(i, j int) bool { return ex[i].Order < ex[j].Order })
+	for _, e := range ex {
+		*doImport = true // import test file whether executed or not
+		if e.Output == "" && !e.EmptyOutput {
+			// Don't run examples with no output.
+			continue
+		}
+		t.Examples = append(t.Examples, testFunc{pkg, "Example" + e.Name, e.Output, e.Unordered})
+		*seen = true
+	}
+	return nil
+}
+
+func checkTestFunc(fset *token.FileSet, fn *ast.FuncDecl, arg string) error {
+	if !isTestFunc(fn, arg) {
+		name := fn.Name.String()
+		pos := fset.Position(fn.Pos())
+		return fmt.Errorf("%s: wrong signature for %s, must be: func %s(%s *testing.%s)", pos, name, name, strings.ToLower(arg), arg)
+	}
+	return nil
+}
+
+var testmainTmpl = template.Must(template.New("main").Parse(`
+package main
+
+import (
+{{if not .TestMain}}
+	"os"
+{{end}}
+	"testing"
+	"testing/internal/testdeps"
+
+{{if .ImportTest}}
+	{{if .NeedTest}}_test{{else}}_{{end}} {{.TestPackage.PkgPath | printf "%q"}}
+{{end}}
+{{if .ImportXtest}}
+	{{if .NeedXtest}}_xtest{{else}}_{{end}} {{.XTestPackage.PkgPath | printf "%q"}}
+{{end}}
+)
+
+var tests = []testing.InternalTest{
+{{range .Tests}}
+	{"{{.Name}}", {{.Package}}.{{.Name}}},
+{{end}}
+}
+
+var benchmarks = []testing.InternalBenchmark{
+{{range .Benchmarks}}
+	{"{{.Name}}", {{.Package}}.{{.Name}}},
+{{end}}
+}
+
+var examples = []testing.InternalExample{
+{{range .Examples}}
+	{"{{.Name}}", {{.Package}}.{{.Name}}, {{.Output | printf "%q"}}, {{.Unordered}}},
+{{end}}
+}
+
+func init() {
+	testdeps.ImportPath = {{.TestPackage.PkgPath | printf "%q"}}
+}
+
+func main() {
+	m := testing.MainStart(testdeps.TestDeps{}, tests, benchmarks, examples)
+{{with .TestMain}}
+	{{.Package}}.{{.Name}}(m)
+{{else}}
+	os.Exit(m.Run())
+{{end}}
+}
+
+`))
diff --git a/go/packages/packages110_test.go b/go/packages/packages110_test.go
index 9bc72a2c..d4005682 100644
--- a/go/packages/packages110_test.go
+++ b/go/packages/packages110_test.go
@@ -6,51 +6,6 @@
 
 package packages_test
 
-import (
-	"bytes"
-	"fmt"
-	"os"
-	"strings"
-	"testing"
-
-	"golang.org/x/tools/go/packages"
-)
-
 func init() {
 	usesOldGolist = true
 }
-
-func TestXTestImports(t *testing.T) {
-	tmp, cleanup := makeTree(t, map[string]string{
-		"src/a/a_test.go": `package a_test; import "a"`,
-		"src/a/a.go":      `package a`,
-	})
-	defer cleanup()
-
-	cfg := &packages.Config{
-		Mode:  packages.LoadImports,
-		Dir:   tmp,
-		Env:   append(os.Environ(), "GOPATH="+tmp, "GO111MODULE=off"),
-		Tests: true,
-	}
-	initial, err := packages.Load(cfg, "a")
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	var gotImports bytes.Buffer
-	for _, pkg := range initial {
-		var imports []string
-		for imp, pkg := range pkg.Imports {
-			imports = append(imports, fmt.Sprintf("%q: %q", imp, pkg.ID))
-		}
-		fmt.Fprintf(&gotImports, "%s {%s}\n", pkg.ID, strings.Join(imports, ", "))
-	}
-	wantImports := `a {}
-a [a.test] {}
-a_test [a.test] {"a": "a [a.test]"}
-`
-	if gotImports.String() != wantImports {
-		t.Fatalf("wrong imports: got <<%s>>, want <<%s>>", gotImports.String(), wantImports)
-	}
-}
diff --git a/go/packages/packages_test.go b/go/packages/packages_test.go
index 6e71dc70..b39e77a5 100644
--- a/go/packages/packages_test.go
+++ b/go/packages/packages_test.go
@@ -152,32 +152,8 @@ func TestLoadImportsGraph(t *testing.T) {
   subdir/d_test [subdir/d.test] -> subdir/d [subdir/d.test]
 `[1:]
 
-	// Legacy go list support does not create test main package.
-	wantOldGraph := `
-  a
-  b
-* c
-* e
-  errors
-  math/bits
-* subdir/d
-* subdir/d [subdir/d.test]
-* subdir/d_test [subdir/d.test]
-  unsafe
-  b -> a
-  b -> errors
-  c -> b
-  c -> unsafe
-  e -> b
-  e -> c
-  subdir/d [subdir/d.test] -> math/bits
-  subdir/d_test [subdir/d.test] -> subdir/d [subdir/d.test]
-`[1:]
-
-	if graph != wantGraph && !usesOldGolist {
+	if graph != wantGraph {
 		t.Errorf("wrong import graph: got <<%s>>, want <<%s>>", graph, wantGraph)
-	} else if graph != wantOldGraph && usesOldGolist {
-		t.Errorf("wrong import graph: got <<%s>>, want <<%s>>", graph, wantOldGraph)
 	}
 
 	// Check node information: kind, name, srcs.
@@ -196,10 +172,6 @@ func TestLoadImportsGraph(t *testing.T) {
 		{"subdir/d.test", "main", "command", "0.go"},
 		{"unsafe", "unsafe", "package", ""},
 	} {
-		if usesOldGolist && test.id == "subdir/d.test" {
-			// Legacy go list support does not create test main package.
-			continue
-		}
 		p, ok := all[test.id]
 		if !ok {
 			t.Errorf("no package %s", test.id)
@@ -261,20 +233,8 @@ func TestLoadImportsGraph(t *testing.T) {
   subdir/d_test [subdir/d.test] -> subdir/d [subdir/d.test]
 `[1:]
 
-		// Legacy go list support does not create test main package.
-		wantOldGraph = `
-  math/bits
-* subdir/d
-* subdir/d [subdir/d.test]
-* subdir/d_test [subdir/d.test]
-* subdir/e
-  subdir/d [subdir/d.test] -> math/bits
-  subdir/d_test [subdir/d.test] -> subdir/d [subdir/d.test]
-`[1:]
-		if graph != wantGraph && !usesOldGolist {
+		if graph != wantGraph {
 			t.Errorf("wrong import graph: got <<%s>>, want <<%s>>", graph, wantGraph)
-		} else if graph != wantOldGraph && usesOldGolist {
-			t.Errorf("wrong import graph: got <<%s>>, want <<%s>>", graph, wantOldGraph)
 		}
 	}
 }