[geary/wip/726281-text-attachment-crlf: 3/13] Add TestCase.assert_null_string method.

[Michael Gratton <mjog src gnome org>]

commit 587e4e75962026ed1846f239dbb68d3d990e3ca5
Author: Michael James Gratton <mike vee net>
Date:   Sat May 5 12:04:26 2018 +1000

    Add TestCase.assert_null_string method.

 test/test-case.vala |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)
---
diff --git a/test/test-case.vala b/test/test-case.vala
index 759962d..1d72561 100644
--- a/test/test-case.vala
+++ b/test/test-case.vala
@@ -62,6 +62,18 @@ public void assert_string(string expected, string? actual, string? context = nul
     }
 }
 
+public void assert_null_string(string? actual, string? context = null)
+    throws Error {
+    if (actual != null) {
+        string a = actual;
+        if (a.length > 70) {
+            a = a[0:70] + "…";
+        }
+        print_assert("Expected: null, was: \"%s\"".printf(a), context);
+        assert_not_reached();
+    }
+}
+
 public void assert_int(int expected, int actual, string? context = null)
     throws Error {
     if (expected != actual) {