add truncate tests

tests/c-truncate.c

@@ -0,0 +1,7 @@
+#include <unistd.h>
+
+int main() {
+  truncate("tmp/foobar", 100); /* should fail because foobar does not exist */
+  truncate("tmp/foo", 100);
+  return 0;
+}

tests/c-truncate.py

@@ -0,0 +1,9 @@
+import tests.helper as th
+
+def passes(out, err):
+    return all(
+        [th.reads(err, '/tests/c-truncate.test'),
+         th.writes(err, '/tmp/foo'),
+         th.count_writes(err, 1),
+         th.count_readdir(err, 0),
+     ])

tests/truncate.py

@@ -0,0 +1,10 @@
+import tests.helper as th
+
+def passes(out, err):
+    return all(
+        [th.reads(err, '/tests/truncate.sh'),
+         th.count_writes(err, 2),
+         th.reads(err, '/tmp/root_symlink'),
+         th.writes(err, '/tmp/foo'),
+         th.writes(err, '/tmp/foobar'),
+     ])

tests/truncate.sh

@@ -0,0 +1,8 @@
+set -ev
+
+cd tmp/root_symlink/tmp
+
+echo foo > foo
+truncate --size 0 foo
+
+truncate --size 0 foobar