diff --git a/src/lib/strconv/testatof.go b/src/lib/strconv/testatof.go
index df3396b..f17e630 100644
--- a/src/lib/strconv/testatof.go
+++ b/src/lib/strconv/testatof.go
@@ -24,6 +24,61 @@
 	Test{ "100000000000000016777216", "1.0000000000000003e+23" },
 	Test{ "-1", "-1" },
 	Test{ "-0", "0" },
+	Test{ "1e-20", "1e-20" },
+
+	// largest float64
+	Test{ "1.7976931348623157e308", "1.7976931348623157e+308" },
+	Test{ "-1.7976931348623157e308", "-1.7976931348623157e+308" },
+	// next float64 - too large
+	Test{ "1.7976931348623159e308", "+Inf" },
+	Test{ "-1.7976931348623159e308", "-Inf" },
+	// the border is ...158079
+	// borderline - okay
+	Test{ "1.7976931348623158e308", "1.7976931348623157e+308" },
+	Test{ "-1.7976931348623158e308", "-1.7976931348623157e+308" },
+	// borderline - too large
+	Test{ "1.797693134862315808e308", "+Inf" },
+	Test{ "-1.797693134862315808e308", "-Inf" },
+
+	// a little too large
+	Test{ "1e308", "1e+308" },
+	Test{ "2e308", "+Inf" },
+	Test{ "1e309", "+Inf" },
+
+	// way too large
+	Test{ "1e310", "+Inf" },
+	Test{ "-1e310", "-Inf" },
+	Test{ "1e400", "+Inf" },
+	Test{ "-1e400", "-Inf" },
+	Test{ "1e400000", "+Inf" },
+	Test{ "-1e400000", "-Inf" },
+
+	// denormalized
+	Test{ "1e-305", "1e-305" },
+	Test{ "1e-306", "1e-306" },
+	Test{ "1e-307", "1e-307" },
+	Test{ "1e-308", "1e-308" },
+	Test{ "1e-309", "1e-309" },
+	Test{ "1e-310", "1e-310" },
+	Test{ "1e-322", "1e-322" },
+	// smallest denormal
+	Test{ "5e-324", "5e-324" },
+	// too small
+	Test{ "4e-324", "0" },
+	// way too small
+	Test{ "1e-350", "0" },
+	Test{ "1e-400000", "0" },
+
+	// try to overflow exponent
+	Test{ "1e-4294967296", "0" },
+	Test{ "1e+4294967296", "+Inf" },
+	Test{ "1e-18446744073709551616", "0" },
+	Test{ "1e+18446744073709551616", "+Inf" },
+
+	// Parse errors
+	Test{ "1e", "error" },
+	Test{ "1e-", "error" },
+	Test{ ".e-1", "error" },
 }
 
 func main() {
@@ -31,8 +86,17 @@
 	for i := 0; i < len(tests); i++ {
 		t := &tests[i];
 		f, overflow, ok := strconv.atof64(t.in);
+		if !ok && t.out == "error" {
+			continue;
+		}
 		if !ok {
-			panicln("test", t.in);
+			panicln("test:", t.in, "failed to parse");
+		}
+		if overflow && !sys.isInf(f, 0) {
+			panicln("overflow but not inf:", t.in, f);
+		}
+		if sys.isInf(f, 0) && !overflow {
+			panicln("inf but not overflow:", t.in, f);
 		}
 		s := strconv.ftoa64(f, 'g', -1);
 		if s != t.out {