diff --git a/test/nil.go b/test/nil.go
index fd938273961..9f7bcbb59fd 100644
--- a/test/nil.go
+++ b/test/nil.go
@@ -4,6 +4,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Test nil.
+
 package main
 
 import (
diff --git a/test/nilptr.go b/test/nilptr.go
index 1a489aae963..b784914e590 100644
--- a/test/nilptr.go
+++ b/test/nilptr.go
@@ -4,6 +4,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Test that the implementation catches nil ptr indirection
+// in a large address space.
+
 package main
 
 import "unsafe"
diff --git a/test/parentype.go b/test/parentype.go
index d7c14f3a26b..eafa076481a 100644
--- a/test/parentype.go
+++ b/test/parentype.go
@@ -4,6 +4,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Test that types can be parenthesized.
+
 package main
 
 func f(interface{})
diff --git a/test/peano.go b/test/peano.go
index 2cc0ac280fa..745f5153f6b 100644
--- a/test/peano.go
+++ b/test/peano.go
@@ -4,6 +4,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Test that heavy recursion works. Simple torture test for
+// segmented stacks: do math in unary by recursion.
+
 package main
 
 type Number *Number
diff --git a/test/printbig.go b/test/printbig.go
index d867bdc646c..6985796f3ab 100644
--- a/test/printbig.go
+++ b/test/printbig.go
@@ -4,6 +4,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Test that big numbers work as constants and print can print them.
+
 package main
 
 func main() {
diff --git a/test/range.go b/test/range.go
index 7921e447ec8..b0f3ae605a9 100644
--- a/test/range.go
+++ b/test/range.go
@@ -4,6 +4,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Test the 'for range' construct.
+
 package main
 
 // test range over channels
diff --git a/test/recover3.go b/test/recover3.go
index f87547fc3ec..98700231ef5 100644
--- a/test/recover3.go
+++ b/test/recover3.go
@@ -4,6 +4,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Test recovering from runtime errors.
+
 package main
 
 import (
diff --git a/test/rename.go b/test/rename.go
index ab61c57f6fe..817a8de79a4 100644
--- a/test/rename.go
+++ b/test/rename.go
@@ -4,70 +4,95 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Test that predeclared names can be redeclared by the user.
+
 package main
 
 import "fmt"
 
 func main() {
 	n :=
-		bool +
+		append +
+			bool +
 			byte +
-			float +
+			complex +
+			complex64 +
+			complex128 +
+			cap +
+			close +
+			delete +
+			error +
+			false +
 			float32 +
 			float64 +
+			imag +
 			int +
 			int8 +
 			int16 +
 			int32 +
 			int64 +
+			len +
+			make +
+			new +
+			nil +
+			panic +
+			print +
+			println +
+			real +
+			recover +
+			rune +
+			string +
+			true +
 			uint +
 			uint8 +
 			uint16 +
 			uint32 +
 			uint64 +
 			uintptr +
-			true +
-			false +
-			iota +
-			nil +
-			cap +
-			len +
-			make +
-			new +
-			panic +
-			print +
-			println
-	if n != 27*28/2 {
-		fmt.Println("BUG: wrong n", n, 27*28/2)
+			iota
+	if n != NUM*(NUM-1)/2 {
+		fmt.Println("BUG: wrong n", n, NUM*(NUM-1)/2)
 	}
 }
 
 const (
-	bool    = 1
-	byte    = 2
-	float   = 3
-	float32 = 4
-	float64 = 5
-	int     = 6
-	int8    = 7
-	int16   = 8
-	int32   = 9
-	int64   = 10
-	uint    = 11
-	uint8   = 12
-	uint16  = 13
-	uint32  = 14
-	uint64  = 15
-	uintptr = 16
-	true    = 17
-	false   = 18
-	iota    = 19
-	nil     = 20
-	cap     = 21
-	len     = 22
-	make    = 23
-	new     = 24
-	panic   = 25
-	print   = 26
-	println = 27
+	append = iota
+	bool
+	byte
+	complex
+	complex64
+	complex128
+	cap
+	close
+	delete
+	error
+	false
+	float32
+	float64
+	imag
+	int
+	int8
+	int16
+	int32
+	int64
+	len
+	make
+	new
+	nil
+	panic
+	print
+	println
+	real
+	recover
+	rune
+	string
+	true
+	uint
+	uint8
+	uint16
+	uint32
+	uint64
+	uintptr
+	NUM
+	iota = 0
 )
diff --git a/test/rename1.go b/test/rename1.go
index 765fba2ac15..48262fd2b55 100644
--- a/test/rename1.go
+++ b/test/rename1.go
@@ -4,11 +4,14 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Verify that renamed identifiers no longer have their old meaning.
+// Does not compile.
+
 package main
 
 func main() {
 	var n byte       // ERROR "not a type|expected type"
-	var y = float(0) // ERROR "cannot call|expected function"
+	var y = float32(0) // ERROR "cannot call|expected function"
 	const (
 		a = 1 + iota // ERROR "string|incompatible types" "convert iota"
 	)
@@ -16,31 +19,43 @@ func main() {
 }
 
 const (
-	bool    = 1
-	byte    = 2
-	float   = 3
-	float32 = 4
-	float64 = 5
-	int     = 6
-	int8    = 7
-	int16   = 8
-	int32   = 9
-	int64   = 10
-	uint    = 11
-	uint8   = 12
-	uint16  = 13
-	uint32  = 14
-	uint64  = 15
-	uintptr = 16
-	true    = 17
-	false   = 18
-	iota    = "abc"
-	nil     = 20
-	cap     = 21
-	len     = 22
-	make    = 23
-	new     = 24
-	panic   = 25
-	print   = 26
-	println = 27
+	append = iota
+	bool
+	byte
+	complex
+	complex64
+	complex128
+	cap
+	close
+	delete
+	error
+	false
+	float32
+	float64
+	imag
+	int
+	int8
+	int16
+	int32
+	int64
+	len
+	make
+	new
+	nil
+	panic
+	print
+	println
+	real
+	recover
+	rune
+	string
+	true
+	uint
+	uint8
+	uint16
+	uint32
+	uint64
+	uintptr
+	NUM
+	iota = "123"
 )
diff --git a/test/reorder.go b/test/reorder.go
index a98fd8cbf0b..007039e8a9b 100644
--- a/test/reorder.go
+++ b/test/reorder.go
@@ -4,7 +4,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Check reordering of assignments.
+// Test reordering of assignments.
 
 package main
 
diff --git a/test/reorder2.go b/test/reorder2.go
index 22fefde5301..d91f1d89531 100644
--- a/test/reorder2.go
+++ b/test/reorder2.go
@@ -4,7 +4,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// derived from fixedbugs/bug294.go
+// Test reorderings; derived from fixedbugs/bug294.go.
 
 package main
 
diff --git a/test/rune.go b/test/rune.go
index 3d3823e68be..c013c471d32 100644
--- a/test/rune.go
+++ b/test/rune.go
@@ -4,6 +4,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Test rune constants, expressions and types.
+// Compiles but does not run.
+
 package rune
 
 var (
diff --git a/test/runtime.go b/test/runtime.go
index 3162b3f13e2..89f59e3edb1 100644
--- a/test/runtime.go
+++ b/test/runtime.go
@@ -4,12 +4,13 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// make sure that even if a file imports runtime,
+// Test that even if a file imports runtime,
 // it cannot get at the low-level runtime definitions
-// known to the compiler.  for normal packages
+// known to the compiler.  For normal packages
 // the compiler doesn't even record the lower case
 // functions in its symbol table, but some functions
 // in runtime are hard-coded into the compiler.
+// Does not compile.
 
 package main