diff --git a/src/math/fpclassify.c b/src/math/fpclassify.c
new file mode 100644
index 0000000..8a43cd6
--- /dev/null
+++ b/src/math/fpclassify.c
@@ -0,0 +1,125 @@
+#include <stdio.h>
+#include <math.h>
+
+#define T(a,b) {__LINE__, a, b},
+#define length(a) (sizeof(a)/sizeof*(a))
+
+static struct {
+	int line;
+	float f;
+	int class;
+} tf[] = {
+	T(0.0/0.0, FP_NAN)
+	T(-0.0/0.0, FP_NAN)
+	T(1/0.0, FP_INFINITE)
+	T(-1/0.0, FP_INFINITE)
+	T(0x1.ffffp127, FP_NORMAL)
+	T(-0x1.ffffp127, FP_NORMAL)
+	T(0x1p-127, FP_SUBNORMAL)
+	T(-0x1p-127, FP_SUBNORMAL)
+	T(0.0, FP_ZERO)
+	T(-0.0, FP_ZERO)
+	T(3.14, FP_NORMAL)
+	T(-42, FP_NORMAL)
+};
+
+static struct {
+	int line;
+	double f;
+	int class;
+} td[] = {
+	T(0.0/0.0, FP_NAN)
+	T(-0.0/0.0, FP_NAN)
+	T(1/0.0, FP_INFINITE)
+	T(-1/0.0, FP_INFINITE)
+	T(0x1.ffffp1023, FP_NORMAL)
+	T(-0x1.ffffp1023, FP_NORMAL)
+	T(0x1p-1023, FP_SUBNORMAL)
+	T(-0x1p-1023, FP_SUBNORMAL)
+	T(0.0, FP_ZERO)
+	T(-0.0, FP_ZERO)
+	T(3.14, FP_NORMAL)
+	T(-42, FP_NORMAL)
+};
+
+static struct {
+	int line;
+	long double f;
+	int class;
+} tl[] = {
+	T(0.0/0.0, FP_NAN)
+	T(-0.0/0.0, FP_NAN)
+	T(1/0.0, FP_INFINITE)
+	T(-1/0.0, FP_INFINITE)
+	T(0x1.ffffp16383L, FP_NORMAL)
+	T(-0x1.ffffp16383L, FP_NORMAL)
+	T(0x1p-16383L, FP_SUBNORMAL)
+	T(-0x1p-16383L, FP_SUBNORMAL)
+	T(0.0, FP_ZERO)
+	T(-0.0, FP_ZERO)
+	T(3.14, FP_NORMAL)
+	T(-42, FP_NORMAL)
+};
+
+static char *strclass(int c)
+{
+#define C(n) case n: return #n;
+	switch (c) {
+	C(FP_NAN)
+	C(FP_INFINITE)
+	C(FP_ZERO)
+	C(FP_SUBNORMAL)
+	C(FP_NORMAL)
+	}
+	return "invalid";
+}
+
+#define error(t,c) err++, printf("%s:%d: (at line %d) %La has class %d (%s), but %s returns %d\n", \
+	__FILE__, __LINE__, t.line, (long double)t.f, t.class, strclass(t.class), #c, c(t.f))
+
+int main()
+{
+	int i;
+	int err = 0;
+
+	for (i = 0; i < length(tf); i++) {
+		if (fpclassify(tf[i].f) != tf[i].class)
+			error(tf[i], fpclassify);
+		if (!!isinf(tf[i].f) != (tf[i].class == FP_INFINITE))
+			error(tf[i], isinf);
+		if (!!isnan(tf[i].f) != (tf[i].class == FP_NAN))
+			error(tf[i], isnan);
+		if (!!isnormal(tf[i].f) != (tf[i].class == FP_NORMAL))
+			error(tf[i], isnormal);
+		if (!!isfinite(tf[i].f) != (tf[i].class > FP_INFINITE))
+			error(tf[i], isfinite);
+	}
+
+	for (i = 0; i < length(td); i++) {
+		if (fpclassify(td[i].f) != td[i].class)
+			error(td[i], fpclassify);
+		if (!!isinf(td[i].f) != (td[i].class == FP_INFINITE))
+			error(td[i], isinf);
+		if (!!isnan(td[i].f) != (td[i].class == FP_NAN))
+			error(td[i], isnan);
+		if (!!isnormal(td[i].f) != (td[i].class == FP_NORMAL))
+			error(td[i], isnormal);
+		if (!!isfinite(td[i].f) != (td[i].class > FP_INFINITE))
+			error(td[i], isfinite);
+	}
+
+	for (i = 0; i < length(tl); i++) {
+		if (fpclassify(tl[i].f) != tl[i].class)
+			error(tl[i], fpclassify);
+		if (!!isinf(tl[i].f) != (tl[i].class == FP_INFINITE))
+			error(tl[i], isinf);
+		if (!!isnan(tl[i].f) != (tl[i].class == FP_NAN))
+			error(tl[i], isnan);
+		if (!!isnormal(tl[i].f) != (tl[i].class == FP_NORMAL))
+			error(tl[i], isnormal);
+		if (!!isfinite(tl[i].f) != (tl[i].class > FP_INFINITE))
+			error(tl[i], isfinite);
+	}
+
+	return !!err;
+}