diff --git a/third_party/double-conversion/double-conversion.mk b/third_party/double-conversion/double-conversion.mk
index a19a123ef..269fafb93 100644
--- a/third_party/double-conversion/double-conversion.mk
+++ b/third_party/double-conversion/double-conversion.mk
@@ -4,13 +4,45 @@
 PKGS += THIRD_PARTY_DOUBLECONVERSION
 
 THIRD_PARTY_DOUBLECONVERSION_ARTIFACTS += THIRD_PARTY_DOUBLECONVERSION_A
-THIRD_PARTY_DOUBLECONVERSION = $(THIRD_PARTY_DOUBLECONVERSION_A_DEPS) $(THIRD_PARTY_DOUBLECONVERSION_A)
+THIRD_PARTY_DOUBLECONVERSION = $(THIRD_PARTY_DOUBLECONVERSION_A_DEPS)	\
+							   $(THIRD_PARTY_DOUBLECONVERSION_A)
 THIRD_PARTY_DOUBLECONVERSION_A = o/$(MODE)/third_party/double-conversion/libdouble-conversion.a
 
 THIRD_PARTY_DOUBLECONVERSION_A_FILES := $(wildcard third_party/double-conversion/*)
 THIRD_PARTY_DOUBLECONVERSION_A_SRCS_CC = $(filter %.cc,$(THIRD_PARTY_DOUBLECONVERSION_A_FILES))
 THIRD_PARTY_DOUBLECONVERSION_A_HDRS = $(filter %.h,$(THIRD_PARTY_DOUBLECONVERSION_A_FILES))
 
+THIRD_PARTY_DOUBLECONVERSION_TEST_COMS = \
+		o/$(MODE)/third_party/double-conversion/double-conversion-tester.com
+
+THIRD_PARTY_DOUBLECONVERSION_TEST_BINS = \
+		$(THIRD_PARTY_DOUBLECONVERSION_TEST_COMS) \
+		$(THIRD_PARTY_DOUBLECONVERSION_TEST_COMS:%=%.dbg)
+
+THIRD_PARTY_DOUBLECONVERSION_TEST_A_SRCS_CC = \
+	third_party/double-conversion/test/cctest.cc	\
+	third_party/double-conversion/test/gay-fixed.cc	\
+	third_party/double-conversion/test/gay-precision.cc	\
+	third_party/double-conversion/test/gay-shortest.cc	\
+	third_party/double-conversion/test/gay-shortest-single.cc	\
+	third_party/double-conversion/test/test-bignum.cc	\
+	third_party/double-conversion/test/test-bignum-dtoa.cc	\
+	third_party/double-conversion/test/test-conversions.cc	\
+	third_party/double-conversion/test/test-diy-fp.cc	\
+	third_party/double-conversion/test/test-dtoa.cc	\
+	third_party/double-conversion/test/test-fast-dtoa.cc	\
+	third_party/double-conversion/test/test-fixed-dtoa.cc	\
+	third_party/double-conversion/test/test-ieee.cc	\
+	third_party/double-conversion/test/test-strtod.cc
+
+THIRD_PARTY_DOUBLECONVERSION_TEST_A_HDRS = \
+	third_party/double-conversion/test/cctest.h	\
+	third_party/double-conversion/test/checks.h	\
+	third_party/double-conversion/test/gay-fixed.h	\
+	third_party/double-conversion/test/gay-precision.h	\
+	third_party/double-conversion/test/gay-shortest.h	\
+	third_party/double-conversion/test/gay-shortest-single.h
+
 THIRD_PARTY_DOUBLECONVERSION_A_OBJS =					\
 	$(THIRD_PARTY_DOUBLECONVERSION_A_SRCS_CC:%.cc=o/$(MODE)/%.o)
 
@@ -18,6 +50,9 @@ THIRD_PARTY_DOUBLECONVERSION_A_CHECKS =					\
 	$(THIRD_PARTY_DOUBLECONVERSION_A).pkg				\
 	$(THIRD_PARTY_DOUBLECONVERSION_A_HDRS:%=o/$(MODE)/%.okk)
 
+THIRD_PARTY_DOUBLECONVERSION_TEST_A_OBJS = \
+	$(THIRD_PARTY_DOUBLECONVERSION_TEST_A_SRCS_CC:%.cc=o/$(MODE)/%.o)
+
 THIRD_PARTY_DOUBLECONVERSION_A_DIRECTDEPS =				\
 	LIBC_INTRIN						\
 	LIBC_NEXGEN32E						\
@@ -29,6 +64,7 @@ THIRD_PARTY_DOUBLECONVERSION_A_DIRECTDEPS =				\
 	LIBC_SYSV						\
 	LIBC_STR						\
 	LIBC_STUBS						\
+	LIBC_UNICODE					\
 	LIBC_TINYMATH						\
 	THIRD_PARTY_GDTOA				\
 	THIRD_PARTY_LIBCXX
@@ -50,6 +86,70 @@ $(THIRD_PARTY_DOUBLECONVERSION_A_OBJS):					\
 			-ffunction-sections			\
 			-fdata-sections
 
+$(THIRD_PARTY_DOUBLECONVERSION_TEST_A_OBJS):			\
+		OVERRIDE_CXXFLAGS +=				\
+			-DSTACK_FRAME_UNLIMITED		\
+			-ffunction-sections			\
+			-fdata-sections
+
+o/$(MODE)/third_party/double-conversion/double-conversion-tester.com.dbg: \
+		$(THIRD_PARTY_DOUBLECONVERSION_A_DEPS)	\
+		$(THIRD_PARTY_DOUBLECONVERSION_A)	\
+		$(THIRD_PARTY_DOUBLECONVERSION_TEST_A_OBJS) \
+		$(CRT)							\
+		$(APE_NO_MODIFY_SELF)
+	@$(APELINK)
+
+THIRD_PARTY_DOUBLECONVERSION_TEST_NAMES = \
+	test-strtod	\
+	test-ieee	\
+	test-fixed-dtoa	\
+	test-fast-dtoa	\
+	test-dtoa	\
+	test-diy-fp	\
+	test-conversions	\
+	test-bignum-dtoa	\
+	test-bignum
+
+THIRD_PARTY_DOUBLECONVERSION_TEST_RUNS = \
+	$(THIRD_PARTY_DOUBLECONVERSION_TEST_NAMES:%=o/$(MODE)/third_party/double-conversion/%.runs)
+
+o/$(MODE)/third_party/double-conversion/test-strtod.runs:	\
+	o/$(MODE)/third_party/double-conversion/double-conversion-tester.com
+	@$(COMPILE) -ACHECK -tT$@ $< test-strtod
+	
+o/$(MODE)/third_party/double-conversion/test-ieee.runs:	\
+	o/$(MODE)/third_party/double-conversion/double-conversion-tester.com
+	@$(COMPILE) -ACHECK -tT$@ $< test-ieee
+	
+o/$(MODE)/third_party/double-conversion/test-fixed-dtoa.runs:	\
+	o/$(MODE)/third_party/double-conversion/double-conversion-tester.com
+	@$(COMPILE) -ACHECK -tT$@ $< test-fixed-dtoa
+	
+o/$(MODE)/third_party/double-conversion/test-fast-dtoa.runs:	\
+	o/$(MODE)/third_party/double-conversion/double-conversion-tester.com
+	@$(COMPILE) -ACHECK -tT$@ $< test-fast-dtoa
+	
+o/$(MODE)/third_party/double-conversion/test-dtoa.runs:	\
+	o/$(MODE)/third_party/double-conversion/double-conversion-tester.com
+	@$(COMPILE) -ACHECK -tT$@ $< test-dtoa
+	
+o/$(MODE)/third_party/double-conversion/test-diy-fp.runs:	\
+	o/$(MODE)/third_party/double-conversion/double-conversion-tester.com
+	@$(COMPILE) -ACHECK -tT$@ $< test-diy-fp
+	
+o/$(MODE)/third_party/double-conversion/test-conversions.runs:	\
+	o/$(MODE)/third_party/double-conversion/double-conversion-tester.com
+	@$(COMPILE) -ACHECK -tT$@ $< test-conversions
+	
+o/$(MODE)/third_party/double-conversion/test-bignum-dtoa.runs:	\
+	o/$(MODE)/third_party/double-conversion/double-conversion-tester.com
+	@$(COMPILE) -ACHECK -tT$@ $< test-bignum-dtoa
+	
+o/$(MODE)/third_party/double-conversion/test-bignum.runs:	\
+	o/$(MODE)/third_party/double-conversion/double-conversion-tester.com
+	@$(COMPILE) -ACHECK -tT$@ $< test-bignum
+	
 THIRD_PARTY_DOUBLECONVERSION_LIBS = $(foreach x,$(THIRD_PARTY_DOUBLECONVERSION_ARTIFACTS),$($(x)))
 THIRD_PARTY_DOUBLECONVERSION_SRCS = $(foreach x,$(THIRD_PARTY_DOUBLECONVERSION_ARTIFACTS),$($(x)_SRCS))
 THIRD_PARTY_DOUBLECONVERSION_HDRS = $(foreach x,$(THIRD_PARTY_DOUBLECONVERSION_ARTIFACTS),$($(x)_HDRS))
@@ -57,4 +157,6 @@ THIRD_PARTY_DOUBLECONVERSION_CHECKS = $(foreach x,$(THIRD_PARTY_DOUBLECONVERSION
 THIRD_PARTY_DOUBLECONVERSION_OBJS = $(foreach x,$(THIRD_PARTY_DOUBLECONVERSION_ARTIFACTS),$($(x)_OBJS))
 
 .PHONY: o/$(MODE)/third_party/double-conversion
-o/$(MODE)/third_party/double-conversion: $(THIRD_PARTY_DOUBLECONVERSION_CHECKS)
+o/$(MODE)/third_party/double-conversion: \
+	$(THIRD_PARTY_DOUBLECONVERSION_CHECKS) \
+	$(THIRD_PARTY_DOUBLECONVERSION_TEST_RUNS)
diff --git a/third_party/double-conversion/test/test-ieee.cc b/third_party/double-conversion/test/test-ieee.cc
index 20018fe19..9191849be 100644
--- a/third_party/double-conversion/test/test-ieee.cc
+++ b/third_party/double-conversion/test/test-ieee.cc
@@ -26,7 +26,7 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include "libc/isystem/stdlib.h"
-#include "libc/isystem/limits"
+#include "third_party/libcxx/limits"
 
 #include "third_party/double-conversion/test/cctest.h"
 #include "third_party/double-conversion/diy-fp.h"