diff --git a/apps/lib/expr.asm b/apps/lib/expr.asm
index 57eb33d..3a17a43 100644
--- a/apps/lib/expr.asm
+++ b/apps/lib/expr.asm
@@ -26,6 +26,18 @@ parseExpr:
 	pop	de
 	ret
 
+; Same as parseExpr, but preserves IX and puts result in DE. This is a
+; transitionary routine and will replace parseExpr when everyone has jumped
+; ship.
+parseExprDE:
+	push	ix
+	push	hl
+	call	_parseExpr
+	push	ix \ pop de
+	pop	hl
+	pop	ix
+	ret
+
 _parseExpr:
 	ld	de, exprTbl
 .loop:
diff --git a/tools/emul/runbin/runbin.c b/tools/emul/runbin/runbin.c
index 2de5bb4..2c5456c 100644
--- a/tools/emul/runbin/runbin.c
+++ b/tools/emul/runbin/runbin.c
@@ -6,9 +6,15 @@
  * until it halts. The return code is the value of the register A at halt time.
  */
 
+static void iowr_stderr(uint8_t val)
+{
+    fputc(val, stderr);
+}
+
 int main()
 {
     Machine *m = emul_init();
+    m->iowr[0] = iowr_stderr;
     // read stdin in mem
     int i = 0;
     int c = getchar();
@@ -22,6 +28,7 @@ int main()
         return 1;
     }
     emul_loop();
+    if (m->cpu.R1.wr.HL)
     return m->cpu.R1.br.A;
 }
 
diff --git a/tools/tests/unit/runtests.sh b/tools/tests/unit/runtests.sh
index 78566c8..c3f0519 100755
--- a/tools/tests/unit/runtests.sh
+++ b/tools/tests/unit/runtests.sh
@@ -11,7 +11,7 @@ APPS="${BASE}/apps"
 
 chk() {
     echo "Running test $1"
-    if ! ${ZASM} "${KERNEL}" "${APPS}" < $1 | ${RUNBIN}; then
+    if ! ${ZASM} "${KERNEL}" "${APPS}" common.asm < $1 | ${RUNBIN}; then
         echo "failed with code ${PIPESTATUS[1]}"
         exit 1
     fi
@@ -22,7 +22,7 @@ if [ ! -z $1 ]; then
     exit 0
 fi
 
-for fn in *.asm; do
+for fn in test_*.asm; do
     chk "${fn}"
 done
 
diff --git a/tools/tests/unit/test_basic_parse.asm b/tools/tests/unit/test_basic_parse.asm
index 6949da5..3c667d1 100644
--- a/tools/tests/unit/test_basic_parse.asm
+++ b/tools/tests/unit/test_basic_parse.asm
@@ -1,5 +1,6 @@
 jp	test
 
+.inc "ascii.h"
 .inc "core.asm"
 .inc "str.asm"
 .inc "lib/util.asm"
@@ -8,6 +9,9 @@ jp	test
 .equ	EXPR_PARSE	parseLiteral
 .inc "lib/expr.asm"
 .inc "basic/parse.asm"
+.inc "lib/fmt.asm"
+.inc "stdio.asm"
+.inc "common.asm"
 
 test:
 	ld	sp, 0xffff
@@ -55,21 +59,21 @@ testParseThruth:
 
 .true:
 	call	parseTruth
-	jp	nz, fail
+	call	assertZ
 	or	a
-	jp	z, fail
+	call	assertNZ
 	jp	nexttest
 
 .false:
 	call	parseTruth
-	jp	nz, fail
+	call	assertZ
 	or	a
-	jp	nz, fail
+	call	assertZ
 	jp	nexttest
 
 .error:
 	call	parseTruth
-	jp	z, fail
+	call	assertNZ
 	jp	nexttest
 
 .t1:	.db	"42", 0
@@ -88,17 +92,4 @@ testParseThruth:
 .f6:	.db	"2<=1", 0
 .e1:	.db	"foo", 0
 
-testNum:	.db 1
-
-nexttest:
-	ld	a, (testNum)
-	inc	a
-	ld	(testNum), a
-	ret
-
-fail:
-	ld	a, (testNum)
-	halt
-
-; used as RAM
-sandbox:
+STDIO_RAMSTART:
diff --git a/tools/tests/unit/test_core.asm b/tools/tests/unit/test_core.asm
index 71e67de..1ae3b06 100644
--- a/tools/tests/unit/test_core.asm
+++ b/tools/tests/unit/test_core.asm
@@ -5,8 +5,14 @@
 
 jp	test
 
+.inc "ascii.h"
+.inc "core.asm"
+.inc "lib/ari.asm"
+.inc "lib/fmt.asm"
+.inc "stdio.asm"
+.inc "common.asm"
+
 dummyLabel:
-testNum:	.db 1
 
 .equ	dummyLabel	0x42
 
@@ -37,37 +43,25 @@ test:
 	call	nexttest
 
 	; Test that .equ can override label
-	ld	a, 0x42
+	ld	de, 0x42
 	ld	hl, dummyLabel
-	cp	l
-	jp	nz, fail
+	call	assertEQW
 	call	nexttest
 
 	; test that "@" is updated by a .org directive
 	ld	hl, AFTER_ORG
 	ld	de, 0x1234
-	or	a	; clear carry
-	sbc	hl, de
-	jp	nz, fail
+	call	assertEQW
 	call	nexttest
 
 	; test that AND affects the Z flag
 	ld	a, 0x69
 	and	0x80
-	jp	nz, fail
+	call	assertZ
 	call	nexttest
 
 	; success
 	xor	a
 	halt
 
-nexttest:
-	ld	a, (testNum)
-	inc	a
-	ld	(testNum), a
-	ret
-
-fail:
-	ld	a, (testNum)
-	halt
-
+STDIO_RAMSTART:
diff --git a/tools/tests/unit/test_expr.asm b/tools/tests/unit/test_expr.asm
index e52ab25..260d42a 100644
--- a/tools/tests/unit/test_expr.asm
+++ b/tools/tests/unit/test_expr.asm
@@ -9,10 +9,12 @@
 
 jp	test
 
+.inc "ascii.h"
 .inc "core.asm"
 .inc "str.asm"
 .inc "lib/util.asm"
 .inc "lib/ari.asm"
+.inc "lib/fmt.asm"
 .inc "zasm/util.asm"
 .inc "zasm/const.asm"
 .inc "lib/parse.asm"
@@ -21,6 +23,9 @@ jp	test
 .inc "zasm/symbol.asm"
 .equ	EXPR_PARSE	parseNumberOrSymbol
 .inc "lib/expr.asm"
+.equ	STDIO_RAMSTART	SYM_RAMEND
+.inc "stdio.asm"
+.inc "common.asm"
 
 ; Pretend that we aren't in first pass
 zasmIsFirstPass:
@@ -29,8 +34,6 @@ zasmIsFirstPass:
 zasmGetPC:
 	ret
 
-testNum:	.db 1
-
 s1:		.db "2+2", 0
 s2:		.db "0x4001+0x22", 0
 s3:		.db "FOO+BAR", 0
@@ -44,29 +47,22 @@ sBAR:		.db "BAR", 0
 test:
 	ld	sp, 0xffff
 
+	; New-style tests
+	;call	testParseExpr
+
 	; Old-style tests, not touching them now.
 	ld	hl, s1
-	call	parseExpr
-	jp	nz, fail
-	push	ix \ pop hl
-	ld	a, h
-	or	a
-	jp	nz, fail
-	ld	a, l
-	cp	4
-	jp	nz, fail
+	call	parseExprDE
+	call	assertZ
+	ld	hl, 4
+	call	assertEQW
 	call	nexttest
 
 	ld	hl, s2
-	call	parseExpr
-	jp	nz, fail
-	push	ix \ pop hl
-	ld	a, h
-	cp	0x40
-	jp	nz, fail
-	ld	a, l
-	cp	0x23
-	jp	nz, fail
+	call	parseExprDE
+	call	assertZ
+	ld	hl, 0x4023
+	call	assertEQW
 	call	nexttest
 
 	; before the next test, let's set up FOO and BAR symbols
@@ -81,55 +77,33 @@ test:
 	jp	nz, fail
 
 	ld	hl, s3
-	call	parseExpr
-	jp	nz, fail
-	push	ix \ pop hl
-	ld	a, h
-	cp	0x40
-	jp	nz, fail
-	ld	a, l
-	cp	0x20
-	jp	nz, fail
+	call	parseExprDE
+	call	assertZ
+	ld	hl, 0x4020
+	call	assertEQW
 	call	nexttest
 
 	ld	hl, s4
-	call	parseExpr
-	jp	nz, fail
-	push	ix \ pop hl
-	ld	a, h
-	or	a
-	jp	nz, fail
-	ld	a, l
-	cp	0x60
-	jp	nz, fail
+	call	parseExprDE
+	call	assertZ
+	ld	hl, 0x60
+	call	assertEQW
 	call	nexttest
 
 	ld	hl, s5
-	call	parseExpr
-	jp	nz, fail
-	push	ix \ pop hl
-	ld	a, h
-	cp	0x3f
-	jp	nz, fail
-	ld	a, l
-	cp	0xfd
-	jp	nz, fail
+	call	parseExprDE
+	call	assertZ
+	ld	hl, 0x3ffd
+	call	assertEQW
 	call	nexttest
 
 	ld	hl, s6
-	call	parseExpr
-	jp	nz, fail
-	push	ix \ pop hl
-	ld	a, h
-	cp	0x40
-	jp	nz, fail
-	ld	a, l
-	cp	0x80
-	jp	nz, fail
+	call	parseExprDE
+	call	assertZ
+	ld	hl, 0x4080
+	call	assertEQW
 	call	nexttest
 
-	; New-style tests
-	call	testParseExpr
 	; success
 	xor	a
 	halt
@@ -151,20 +125,18 @@ testParseExpr:
 	call	.testEQ
 	ld	iy, .t8
 	call	.testEQ
+	ld	iy, .t9
+	call	.testEQ
 	ret
 
 .testEQ:
 	push	iy \ pop hl
 	inc	hl \ inc hl
-	call	parseExpr
-	jp	nz, fail
-	push	ix \ pop de
-	ld	a, e
-	cp	(iy)
-	jp	nz, fail
-	ld	a, d
-	cp	(iy+1)
-	jp	nz, fail
+	call	parseExprDE
+	call	assertZ
+	ld	l, (iy)
+	ld	h, (iy+1)
+	call	assertEQW
 	jp	nexttest
 
 .t1:
@@ -191,13 +163,6 @@ testParseExpr:
 .t8:
 	.dw	0xffff
 	.db	"-1", 0
-
-nexttest:
-	ld	a, (testNum)
-	inc	a
-	ld	(testNum), a
-	ret
-
-fail:
-	ld	a, (testNum)
-	halt
+.t9:
+	.dw	10
+	.db	"2*3+4", 0