std.debug.assert: remove special case for test builds

Previously, std.debug.assert would `@panic` in test builds,
if the assertion failed. Now, it's always `unreachable`.

This makes release mode test builds more accurately test
the actual code that will be run.

However this requires tests to call `std.testing.expect`
rather than `std.debug.assert` to make sure output is correct.

Here is the explanation of when to use either one, copied from
the assert doc comments:

Inside a test block, it is best to use the `std.testing` module
rather than assert, because assert may not detect a test failure
in ReleaseFast and ReleaseSafe mode. Outside of a test block, assert
is the correct function to use.

closes #1304

1 files changed, 3 insertions, 3 deletions

diff --git a/std/cstr.zig b/std/cstr.zig
index a8aaf21279..abd2eac48f 100644
--- a/std/cstr.zig
+++ b/std/cstr.zig
@@ -2,7 +2,7 @@ const std = @import("index.zig");
 const builtin = @import("builtin");
 const debug = std.debug;
 const mem = std.mem;
-const assert = debug.assert;
+const testing = std.testing;
 
 pub const line_sep = switch (builtin.os) {
     builtin.Os.windows => "\r\n",
@@ -42,8 +42,8 @@ test "cstr fns" {
 }
 
 fn testCStrFnsImpl() void {
-    assert(cmp(c"aoeu", c"aoez") == -1);
-    assert(len(c"123456789") == 9);
+    testing.expect(cmp(c"aoeu", c"aoez") == -1);
+    testing.expect(len(c"123456789") == 9);
 }
 
 /// Returns a mutable slice with 1 more byte of length which is a null byte.