Unittest prep: Move get_yesterday_date_str() to helper file.

We want to use this function in our guardfraction unittests, so make a
test_helpers module and move it there.

src/test/include.am

@@ -61,6 +61,7 @@ src_test_test_SOURCES = \
 	src/test/test_status.c \
 	src/test/test_threads.c \
 	src/test/test_util.c \
+	src/test/test_helpers.c \
 	src/test/testing_common.c \
 	src/ext/tinytest.c
 
@@ -119,6 +120,7 @@ src_test_test_workqueue_LDADD = src/or/libtor-testing.a \
 noinst_HEADERS+= \
 	src/test/fakechans.h \
 	src/test/test.h \
+	src/test/test_helpers.h \
 	src/test/test_descriptors.inc \
 	src/test/example_extrainfo.inc \
 	src/test/failing_routerdescs.inc \

src/test/test_entrynodes.c

@@ -19,6 +19,7 @@
 #include "config.h"
 
 #include "test_descriptors.inc"
+#include "test_helpers.h"
 
 /* TODO:
  * choose_random_entry() test with state set.
@@ -326,19 +327,6 @@ state_lines_free(smartlist_t *entry_guard_lines)
   smartlist_free(entry_guard_lines);
 }
 
-/* Return a statically allocated string representing yesterday's date
- * in ISO format. We use it so that state file items are not found to
- * be outdated. */
-static const char *
-get_yesterday_date_str(void)
-{
-  static char buf[ISO_TIME_LEN+1];
-
-  time_t yesterday = time(NULL) - 24*60*60;
-  format_iso_time(buf, yesterday);
-  return buf;
-}
-
 /* Tests entry_guards_parse_state(). It creates a fake Tor state with
    a saved entry guard and makes sure that Tor can parse it and
    creates the right entry node out of it.

src/test/test_helpers.c

@@ -0,0 +1,26 @@
+/* Copyright (c) 2014, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file test_helpers.c
+ * \brief Some helper functions to avoid code duplication in unit tests.
+ */
+
+#include "orconfig.h"
+#include "or.h"
+
+#include "test_helpers.h"
+
+/* Return a statically allocated string representing yesterday's date
+ * in ISO format. We use it so that state file items are not found to
+ * be outdated. */
+const char *
+get_yesterday_date_str(void)
+{
+  static char buf[ISO_TIME_LEN+1];
+
+  time_t yesterday = time(NULL) - 24*60*60;
+  format_iso_time(buf, yesterday);
+  return buf;
+}
+

src/test/test_helpers.h

@@ -0,0 +1,10 @@
+/* Copyright (c) 2014, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#ifndef TOR_TEST_HELPERS_H
+#define TOR_TEST_HELPERS_H
+
+const char *get_yesterday_date_str(void);
+
+#endif
+