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, 2 insertions, 2 deletions

diff --git a/doc/docgen.zig b/doc/docgen.zig
index 14e4700553..7aaf5ebdc7 100644
--- a/doc/docgen.zig
+++ b/doc/docgen.zig
@@ -4,7 +4,7 @@ const io = std.io;
 const os = std.os;
 const warn = std.debug.warn;
 const mem = std.mem;
-const assert = std.debug.assert;
+const testing = std.testing;
 
 const max_doc_file_size = 10 * 1024 * 1024;
 
@@ -620,7 +620,7 @@ const TermState = enum {
 test "term color" {
     const input_bytes = "A\x1b[32;1mgreen\x1b[0mB";
     const result = try termColor(std.debug.global_allocator, input_bytes);
-    assert(mem.eql(u8, result, "A<span class=\"t32\">green</span>B"));
+    testing.expectEqualSlices(u8, "A<span class=\"t32\">green</span>B", result));
 }
 
 fn termColor(allocator: *mem.Allocator, input: []const u8) ![]u8 {