diff --git a/cmd/ssadump/main.go b/cmd/ssadump/main.go
index 3d1dea1..8c4dbd1 100644
--- a/cmd/ssadump/main.go
+++ b/cmd/ssadump/main.go
@@ -49,14 +49,13 @@
 
 Examples:
 % ssadump -build=F hello.go              # dump SSA form of a single package
+% ssadump -build=F -test fmt             # dump SSA form of a package and its tests
 % ssadump -run -interp=T hello.go        # interpret a program, with tracing
-% ssadump -run -test unicode -- -test.v  # interpret the unicode package's tests, verbosely
 ` + loader.FromArgsUsage +
 	`
-When -run is specified, ssadump will run the program.
-The entry point depends on the -test flag:
-if clear, it runs the first package named main.
-if set, it runs the tests of each package.
+The -run flag causes ssadump to run the first package named main.
+
+Interpretation of the standard "testing" package is no longer supported.
 `
 
 func main() {
diff --git a/go/ssa/interp/external.go b/go/ssa/interp/external.go
index f428e58..66727d8 100644
--- a/go/ssa/interp/external.go
+++ b/go/ssa/interp/external.go
@@ -138,9 +138,7 @@
 		"sync/atomic.LoadUint64":           ext۰atomic۰LoadUint64,
 		"sync/atomic.StoreInt64":           ext۰atomic۰StoreInt64,
 		"sync/atomic.StoreUint64":          ext۰atomic۰StoreUint64,
-		"testing.callerEntry":              ext۰testing۰callerEntry,
-		"testing.callerName":               ext۰testing۰callerName,
-		"testing.runExample":               ext۰testing۰runExample,
+		"testing.MainStart":                ext۰testing۰MainStart,
 		"time.Sleep":                       ext۰time۰Sleep,
 		"time.now":                         ext۰time۰now,
 	} {
@@ -512,35 +510,6 @@
 	return uintptr(unsafe.Pointer(f))
 }
 
-// This is a workaround for a bug in go/ssa/testmain.go: it creates
-// InternalExamples even for Example functions with no Output comment.
-// TODO(adonovan): fix (and redesign) testmain.go..
-func ext۰testing۰runExample(fr *frame, args []value) value {
-	// This is a stripped down runExample that simply calls the function.
-	// It does not capture and compare output nor recover from panic.
-	//
-	// func runExample(eg testing.InternalExample) bool {
-	//     eg.F()
-	//     return true
-	// }
-	F := args[0].(structure)[1]
-	call(fr.i, fr, 0, F, nil)
-	return true
-}
-
-// These two internal functions must be faked to avoid calls to
-// runtime.CallersFrames, which is hard to emulate. We are inching
-// towards the point at which I blow away this entire package, or at
-// least all tests that interpret the standard "testing" package.
-
-func ext۰testing۰callerEntry(fr *frame, args []value) value {
-	return uintptr(0) // bogus implementation for now
-}
-
-func ext۰testing۰callerName(fr *frame, args []value) value {
-	return "<unknown>" // bogus implementation for now
-}
-
 func ext۰time۰now(fr *frame, args []value) value {
 	nano := time.Now().UnixNano()
 	return tuple{int64(nano / 1e9), int32(nano % 1e9), int64(0)}
@@ -559,3 +528,10 @@
 	}
 	return b
 }
+
+func ext۰testing۰MainStart(fr *frame, args []value) value {
+	// We no longer support interpretation of the "testing" package
+	// because it changes too often and uses low-level features that
+	// are a pain to emulate.
+	panic(`interpretation of the "testing" package is no longer supported`)
+}
diff --git a/go/ssa/interp/interp.go b/go/ssa/interp/interp.go
index 4c8602d..c092960 100644
--- a/go/ssa/interp/interp.go
+++ b/go/ssa/interp/interp.go
@@ -20,11 +20,13 @@
 //
 // * The reflect package is only partially implemented.
 //
-// * "sync/atomic" operations are not currently atomic due to the
-// "boxed" value representation: it is not possible to read, modify
-// and write an interface value atomically.  As a consequence, Mutexes
-// are currently broken.  TODO(adonovan): provide a metacircular
-// implementation of Mutex avoiding the broken atomic primitives.
+// * The "testing" package is no longer supported because it
+// depends on low-level details that change too often.
+//
+// * "sync/atomic" operations are not atomic due to the "boxed" value
+// representation: it is not possible to read, modify and write an
+// interface value atomically. As a consequence, Mutexes are currently
+// broken.
 //
 // * recover is only partially implemented.  Also, the interpreter
 // makes no attempt to distinguish target panics from interpreter
diff --git a/go/ssa/interp/interp_test.go b/go/ssa/interp/interp_test.go
index 6e9f7b2..2683a28 100644
--- a/go/ssa/interp/interp_test.go
+++ b/go/ssa/interp/interp_test.go
@@ -152,27 +152,6 @@
 	"callstack.go",
 }
 
-// These are files and packages in $GOROOT/src/.
-var gorootSrcTests = []string{
-	"encoding/ascii85",
-	"encoding/hex",
-	// "encoding/pem", // TODO(adonovan): implement (reflect.Value).SetString
-	// "testing",      // TODO(adonovan): implement runtime.Goexit correctly
-	// "hash/crc32",   // TODO(adonovan): implement hash/crc32.haveCLMUL
-	// "log",          // TODO(adonovan): implement runtime.Callers correctly
-
-	// Too slow:
-	// "container/ring",
-	// "hash/adler32",
-
-	"unicode/utf8",
-	"path",
-	"flag",
-	"encoding/csv",
-	"text/scanner",
-	"unicode",
-}
-
 type successPredicate func(exitcode int, output string) error
 
 func run(t *testing.T, dir, input string, success successPredicate) bool {
@@ -312,53 +291,9 @@
 			failures = append(failures, input)
 		}
 	}
-	for _, input := range gorootSrcTests {
-		if !run(t, filepath.Join(build.Default.GOROOT, "src")+slash, input, success) {
-			failures = append(failures, input)
-		}
-	}
 	printFailures(failures)
 }
 
-// TestTestmainPackage runs the interpreter on a synthetic "testmain" package.
-func TestTestmainPackage(t *testing.T) {
-	if testing.Short() {
-		t.Skip() // too slow on some platforms
-	}
-
-	success := func(exitcode int, output string) error {
-		if exitcode == 0 {
-			return fmt.Errorf("unexpected success")
-		}
-		if !strings.Contains(output, "FAIL: TestFoo") {
-			return fmt.Errorf("missing failure log for TestFoo")
-		}
-		if !strings.Contains(output, "FAIL: TestBar") {
-			return fmt.Errorf("missing failure log for TestBar")
-		}
-		// TODO(adonovan): test benchmarks too
-		return nil
-	}
-	run(t, "testdata"+slash, "a_test.go", success)
-
-	// Run a test with a custom TestMain function and ensure that it
-	// is executed, and that m.Run runs the tests.
-	success = func(exitcode int, output string) error {
-		if exitcode != 0 {
-			return fmt.Errorf("unexpected failure; output=%s", output)
-		}
-		if want := `TestMain start
-TestC
-PASS
-TestMain end
-`; output != want {
-			return fmt.Errorf("output was %q, want %q", output, want)
-		}
-		return nil
-	}
-	run(t, "testdata"+slash, "c_test.go", success)
-}
-
 // CreateTestMainPackage should return nil if there were no tests.
 func TestNullTestmainPackage(t *testing.T) {
 	var conf loader.Config