diff --git a/sys/src/libmp/test/convtest.c b/sys/src/libmp/test/convtest.c
new file mode 100644
index 000000000..d3721dfa7
--- /dev/null
+++ b/sys/src/libmp/test/convtest.c
@@ -0,0 +1,124 @@
+#include <u.h>
+#include <libc.h>
+#include <mp.h>
+
+/* these tests suck but better than nothing... but really should test more values than just 1<<i */
+
+#define MPTOX(_name,_type,_func)  \
+void \
+_name(void) \
+{ \
+	mpint *m; \
+	int i, sign, mag; \
+	_type v, e; \
+	int fail; \
+	 \
+	fail = 0; \
+	m = mpnew(0); \
+	for(i = 0; i < 256; i++){ \
+		sign = i >= 128 ? -1 : 1; \
+		mag = i % 128; \
+		itomp(sign, m); \
+		mpleft(m, mag, m); \
+		v = _func(m); \
+		e = 0xcafebabe; USED(e);
+#define MPTOX_END(_func,_format)  \
+		if(v != e){ \
+			fprint(2, "FAIL: _func(%#B): return value: got "_format", expected "_format"\n", m, v, e); \
+			fail=1; \
+		} \
+	} \
+	mpfree(m); \
+	if(!fail) \
+		fprint(2, "_func: passed\n"); \
+}
+
+#define XTOMP(_name,_type,_func)  \
+void \
+_name(void) \
+{ \
+	mpint *m, *r; \
+	int i, sign, mag; \
+	_type v; \
+	int fail; \
+	 \
+	fail = 0; \
+	m = mpnew(0); \
+	r = mpnew(0); \
+	for(i = 0; i < 256; i++){ \
+		sign = i >= 128 ? -1 : 1; \
+		mag = i % 128; \
+		itomp(sign, r); \
+		mpleft(r, mag, r);
+#define XTOMP_END(_func,_type,_format)  \
+		_func(sign * ((_type)1<<mag), m); \
+		if(mpcmp(r, m) != 0){ \
+			fprint(2, "FAIL: _func("_format"): return value: got %#B, expected %#B\n", sign * ((_type)1<<mag), m, r); \
+			fail=1; \
+		} \
+	} \
+	mpfree(m); \
+	mpfree(r); \
+	if(!fail) \
+		fprint(2, "_func: passed\n"); \
+}
+
+MPTOX(test_mptoi, int, mptoi)
+	if(mag < 31)
+		e = sign*(1<<mag);
+	else
+		e = sign > 0 ? (1<<31)-1 : 1<<31;
+MPTOX_END(mptoi, "%#x")
+
+MPTOX(test_mptoui, uint, mptoui)
+	if(mag < 32 && sign > 0)
+		e = 1<<mag;
+	else
+		e = sign > 0 ? -1 : 0;
+MPTOX_END(mptoui, "%#ux")
+
+
+MPTOX(test_mptov, vlong, mptov)
+	if(mag < 63)
+		e = sign*(1LL<<mag);
+	else
+		e = sign > 0 ? (1LL<<63)-1 : 1LL<<63;
+MPTOX_END(mptov, "%#llx")
+
+MPTOX(test_mptouv, uvlong, mptouv)
+	if(mag < 64 && sign > 0)
+		e = 1LL<<mag;
+	else
+		e = sign > 0 ? -1ULL : 0;
+MPTOX_END(mptouv, "%#llux")
+
+XTOMP(test_itomp, int, itomp)
+	if(mag >= 31) continue;
+XTOMP_END(vtomp, vlong, "%lld")
+
+XTOMP(test_uitomp, uint, uitomp)
+	if(mag >= 32 || sign < 0) continue;
+XTOMP_END(uitomp, uint, "%lld")
+
+XTOMP(test_vtomp, vlong, vtomp)
+	if(mag >= 63) continue;
+XTOMP_END(vtomp, vlong, "%lld")
+
+XTOMP(test_uvtomp, uvlong, uvtomp)
+	if(mag >= 64 || sign < 0) continue;
+XTOMP_END(uvtomp, vlong, "%lld")
+
+
+void
+convtests(void)
+{
+	test_mptoi();
+	test_mptoui();
+	test_mptov();
+	test_mptouv();
+	test_itomp();
+	test_uitomp();
+	test_vtomp();
+	test_uvtomp();
+}
+
diff --git a/sys/src/libmp/test/fns.h b/sys/src/libmp/test/fns.h
index c70d1c27e..30f12ecf5 100644
--- a/sys/src/libmp/test/fns.h
+++ b/sys/src/libmp/test/fns.h
@@ -6,3 +6,4 @@ mpint* ldtomp(ldint *, mpint *);
 void mptarget(mpint *);
 void tests(void);
 void mpdiv_(mpint *, mpint *, mpint *, mpint *);
+void convtests(void);
diff --git a/sys/src/libmp/test/main.c b/sys/src/libmp/test/main.c
index e9f0ba6f5..bf2ac6ec2 100644
--- a/sys/src/libmp/test/main.c
+++ b/sys/src/libmp/test/main.c
@@ -48,5 +48,6 @@ main()
 	fmtinstall(L'β', mpdetfmt);
 	fmtinstall('L', ldfmt);
 	
+	convtests();
 	tests();
 }
diff --git a/sys/src/libmp/test/mkfile b/sys/src/libmp/test/mkfile
index 87cb46f5b..bfbdd6948 100644
--- a/sys/src/libmp/test/mkfile
+++ b/sys/src/libmp/test/mkfile
@@ -5,6 +5,7 @@ OFILES=\
 	main.$O\
 	ld.$O\
 	gen.tab.$O\
+	convtest.$O\
 
 HFILES=dat.h fns.h