I am testing the CryptoDESTest.  I am getting some strange behavior.  When I 
run the following code in a Workspace, repeatably, I get the same results:

code:

	| plain key d |
	plain := 'squeaker'.
	key := 'hacking!'.
	Transcript cr; show: 'plain: ', plain printString.
	d := DES key: key.
	d encryptBlock: plain.
	Transcript cr; show: 'plain: ', plain printString.
	self assert: plain asByteArray = #[64 222 70 13 59 145 76 186].
	plain destroy.

output:

plain: 'squeaker'
plain: '@ÞF
;‘Lº'
plain: 'squeaker'
plain: '@ÞF
;‘Lº'
plain: 'squeaker'
plain: '@ÞF
;‘Lº'

However, when I run this as a test method:

testDES3
	| plain key d |
	plain := 'squeaker'.
	key := 'hacking!'.
	Transcript cr; show: 'plain: ', plain printString.
	d := DES key: key.
	d encryptBlock: plain.
	Transcript cr; show: 'plain: ', plain printString.
	self assert: plain asByteArray = #[64 222 70 13 59 145 76 186].
                plain destroy.

I get the following output and the test fails:

plain: 'squeaker'
plain: '@ÞF
;‘Lº'
plain: '        '
plain: '£ƒ¼ïùmÞ$'
plain: '£ƒ¼ïùmÞ$'
plain: '§,}ºé¨öú'
plain: '§,}ºé¨öú'
plain: '3qX¦wRË|'
plain: '3qX¦wRË|'
plain: 'Ê0ê^ó{ì'
plain: 'Ê0ê^ó{ì'
plain: 'çî³›,ίw'

Why is test runner remembering the old value and not setting it with: plain 
:= 'squeaker'.?

TIA,
Rob