diff --git a/test/copy_flash.c b/test/copy_flash.c
index 5c40b53..d39ef93 100644
--- a/test/copy_flash.c
+++ b/test/copy_flash.c
@@ -66,7 +66,7 @@
 		goto free;
 	}
 
-	rc = tmpf_init(&tmp, "flashXXXXXX");
+	rc = tmpf_init(&tmp, "flash-store.XXXXXX");
 	if (rc < 0)
 		goto free;
 
diff --git a/test/erase_flash.c b/test/erase_flash.c
index 71e87b5..fa8c92c 100644
--- a/test/erase_flash.c
+++ b/test/erase_flash.c
@@ -42,7 +42,7 @@
 {
 	int rc;
 
-	rc = tmpf_init(&mtd, "flashXXXXXX");
+	rc = tmpf_init(&mtd, "flash-store.XXXXXX");
 	if (rc < 0)
 		return NULL;
 
diff --git a/test/mbox.c b/test/mbox.c
index dc049ce..6fe7277 100644
--- a/test/mbox.c
+++ b/test/mbox.c
@@ -216,13 +216,13 @@
 
 	atexit(cleanup);
 
-	rc = tmpf_init(&test.mbox, "mboxXXXXXX");
+	rc = tmpf_init(&test.mbox, "mbox-store.XXXXXX");
 	assert(rc == 0);
 
-	rc = tmpf_init(&test.flash, "flashXXXXXX");
+	rc = tmpf_init(&test.flash, "flash-store.XXXXXX");
 	assert(rc == 0);
 
-	rc = tmpf_init(&test.lpc, "lpcXXXXXX");
+	rc = tmpf_init(&test.lpc, "lpc-store.XXXXXX");
 	assert(rc == 0);
 
 	test.context.windows.num = n_windows;
diff --git a/test/tmpf.c b/test/tmpf.c
index 285f5d5..e9cc558 100644
--- a/test/tmpf.c
+++ b/test/tmpf.c
@@ -25,9 +25,12 @@
 
 #include "test/tmpf.h"
 
+static const char *tmpf_dir = "/tmp/";
+
 int tmpf_init(struct tmpf *tmpf, const char *template)
 {
-	strncpy(tmpf->path, template, sizeof(tmpf->path) - 1);
+	strcpy(tmpf->path, tmpf_dir);
+	strncat(tmpf->path, template, sizeof(tmpf->path) - sizeof(tmpf_dir));
 
 	tmpf->fd = mkstemp(tmpf->path);
 	if (tmpf->fd < 0) {
diff --git a/test/tmpf.h b/test/tmpf.h
index ce47191..cb1bda4 100644
--- a/test/tmpf.h
+++ b/test/tmpf.h
@@ -27,8 +27,20 @@
 	char path[PATH_MAX];
 };
 
+/**
+ * Initialise a tmpf instance for use, creating a temporary file.
+ *
+ * @tmpf: A context to initialise with the provided template
+ * @template_str: A file basename in mkstemp(3) template form
+ *
+ * Returns 0 on success, or -1 on error with errno set appropriately
+ */
 int tmpf_init(struct tmpf *tmpf, const char *template_str);
 
+/**
+ * Destroy a tmpf instance, closing the file descriptor and removing the
+ * temporary file.
+ */
 void tmpf_destroy(struct tmpf *tmpf);
 
 #endif /* MBOX_TEST_UTILS_H */
diff --git a/test/write_flash.c b/test/write_flash.c
index ebd0fb7..6a92d4b 100644
--- a/test/write_flash.c
+++ b/test/write_flash.c
@@ -40,7 +40,7 @@
 {
 	int rc;
 
-	rc = tmpf_init(tmp, "flashXXXXXX");
+	rc = tmpf_init(tmp, "flash-store.XXXXXX");
 	if (rc < 0)
 		return NULL;