diff --git a/1-lang0py/.gitignore b/1-lang0py/.gitignore
index deaa674..9bb2af4 100644
--- a/1-lang0py/.gitignore
+++ b/1-lang0py/.gitignore
@@ -2,3 +2,4 @@
 /lang0py*.exe
 /lang0py*.o
 /lang0py*.py
+/lang0py*.py.tmp
diff --git a/1-lang0py/Makefile b/1-lang0py/Makefile
index 6d00386..6214671 100644
--- a/1-lang0py/Makefile
+++ b/1-lang0py/Makefile
@@ -18,18 +18,22 @@ all: lang0py.exe
 	$(CYTHON) -3 --embed $<
 
 lang0py0.py: lang0py.lang0 $(LANG0PY)
-	cat $< | $(LANG0PY) > $@
+	cat $< | $(LANG0PY) > $@.tmp
+	mv $@.tmp $@
 
 lang0py1.py: lang0py.lang0 lang0py0.exe
-	cat $< | ./lang0py0.exe > $@
+	cat $< | ./lang0py0.exe > $@.tmp
+	mv $@.tmp $@
 # Cannot diff on the first iteration - platform change
 
 lang0py2.py: lang0py.lang0 lang0py1.exe
-	cat $< | ./lang0py1.exe > $@
+	cat $< | ./lang0py1.exe > $@.tmp
+	mv $@.tmp $@
 	-diff lang0py1.py lang0py2.py
 
 lang0py.py: lang0py.lang0 lang0py2.exe
-	cat $< | ./lang0py2.exe > $@
+	cat $< | ./lang0py2.exe > $@.tmp
+	mv $@.tmp $@
 	-diff lang0py2.py lang0py.py
 
 clean:
diff --git a/2-lang0c/.gitignore b/2-lang0c/.gitignore
index f7bb4b3..5f9970f 100644
--- a/2-lang0c/.gitignore
+++ b/2-lang0c/.gitignore
@@ -1,4 +1,5 @@
 /lang0c*.c
+/lang0c*.c.tmp
 /lang0c*.exe
 /lang0c*.o
 /lang0c*.py
diff --git a/2-lang0c/Makefile b/2-lang0c/Makefile
index c8ec277..0e9fe54 100644
--- a/2-lang0c/Makefile
+++ b/2-lang0c/Makefile
@@ -15,7 +15,8 @@ all: lang0c.exe
 	gcc -c $<
 
 lang0c0.py: lang0c.lang0 $(LANG0PY)
-	cat $< | $(LANG0PY) > $@
+	cat $< | $(LANG0PY) > $@.tmp
+	mv $@.tmp $@
 
 lang0c0.c: lang0c0.py
 	$(CYTHON) -3 --embed $<
@@ -27,15 +28,18 @@ lang0c0.exe: lang0c0.o
 	gcc -o $@ $< -lpython$(PYVERSION)
 
 lang0c1.c: lang0c.lang0 lang0c0.exe
-	cat $< | ./lang0c0.exe > $@
+	cat $< | ./lang0c0.exe > $@.tmp
+	mv $@.tmp $@
 # Cannot diff on the first iteration - platform change
 
 lang0c2.c: lang0c.lang0 lang0c1.exe
-	cat $< | ./lang0c1.exe > $@
+	cat $< | ./lang0c1.exe > $@.tmp
+	mv $@.tmp $@
 	-diff lang0c1.c lang0c2.c
 
 lang0c.c: lang0c.lang0 lang0c2.exe
-	cat $< | ./lang0c2.exe > $@
+	cat $< | ./lang0c2.exe > $@.tmp
+	mv $@.tmp $@
 	-diff lang0c2.c lang0c.c
 
 clean:
diff --git a/tests/Makefile b/tests/Makefile
index 8701ecc..510228f 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -1,5 +1,7 @@
 .SUFFIXES:
 .PHONY: all clean
+.PRECIOUS: build/%.it0.py build/%.it0.c
+.DELETE_ON_ERROR:
 
 PYVERSION=3.10
 PYPREFIX=/usr
@@ -31,8 +33,12 @@ clean:
 ###
 # it0
 
+../0-lang0py/lang0py.exe: ../0-lang0py/lang0py.py
+	$(MAKE) -C ../0-lang0py
+
 build/%.it0.py: %.lang0 ../0-lang0py/lang0py.exe
-	cat $< | ../0-lang0py/lang0py.exe > $@
+	cat $< | ../0-lang0py/lang0py.exe > $@.tmp
+	mv $@.tmp $@
 
 build/%.it0.c: build/%.it0.py
 	$(CYTHON) -3 --embed -o $@ $^
@@ -46,8 +52,12 @@ build/%.it0: build/%.it0.o
 ###
 # it1
 
+../1-lang0py/lang0py.exe: ../0-lang0py/lang0py.exe ../1-lang0py/lang0py.lang0
+	$(MAKE) -C ../1-lang0py
+
 build/%.it1.py: %.lang0 ../1-lang0py/lang0py.exe
-	cat $< | ../1-lang0py/lang0py.exe > $@
+	cat $< | ../1-lang0py/lang0py.exe > $@.tmp
+	mv $@.tmp $@
 
 build/%.it1.c: build/%.it1.py
 	$(CYTHON) -3 --embed -o $@ $^
@@ -61,8 +71,12 @@ build/%.it1: build/%.it1.o
 ###
 # it2
 
+../2-lang0c/lang0c.exe: ../0-lang0py/lang0py.exe ../1-lang0py/lang0py.exe ../2-lang0c/lang0c.lang0
+	$(MAKE) -C ../2-lang0c
+
 build/%.it2.c: %.lang0 ../2-lang0c/lang0c.exe
-	cat $< | ../2-lang0c/lang0c.exe > $@
+	cat $< | ../2-lang0c/lang0c.exe > $@.tmp
+	mv $@.tmp $@
 
 build/%.it2.o: build/%.it2.c
 	$(CC) -o $@ -c $^ -I$(PYPREFIX)/include/python$(PYVERSION)
diff --git a/tests/build/.gitignore b/tests/build/.gitignore
index 3ee26ee..4dfaadf 100644
--- a/tests/build/.gitignore
+++ b/tests/build/.gitignore
@@ -2,10 +2,13 @@
 /*.it0.c
 /*.it0.o
 /*.it0.py
+/*.it0.py.tmp
 /*.it1
 /*.it1.c
 /*.it1.o
 /*.it1.py
+/*.it1.py.tmp
 /*.it2
 /*.it2.c
+/*.it2.c.tmp
 /*.it2.o