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, 12 insertions, 11 deletions

diff --git a/src-self-hosted/arg.zig b/src-self-hosted/arg.zig
index 99e6ecc17a..7bbd233a75 100644
--- a/src-self-hosted/arg.zig
+++ b/src-self-hosted/arg.zig
@@ -1,5 +1,6 @@
 const std = @import("std");
 const debug = std.debug;
+const testing = std.testing;
 const mem = std.mem;
 
 const Allocator = mem.Allocator;
@@ -272,21 +273,21 @@ test "parse arguments" {
 
     var args = try Args.parse(std.debug.global_allocator, spec1, cliargs);
 
-    debug.assert(args.present("help"));
-    debug.assert(!args.present("help2"));
-    debug.assert(!args.present("init"));
+    testing.expect(args.present("help"));
+    testing.expect(!args.present("help2"));
+    testing.expect(!args.present("init"));
 
-    debug.assert(mem.eql(u8, args.single("build-file").?, "build.zig"));
-    debug.assert(mem.eql(u8, args.single("color").?, "on"));
+    testing.expect(mem.eql(u8, args.single("build-file").?, "build.zig"));
+    testing.expect(mem.eql(u8, args.single("color").?, "on"));
 
     const objects = args.many("object").?;
-    debug.assert(mem.eql(u8, objects[0], "obj1"));
-    debug.assert(mem.eql(u8, objects[1], "obj2"));
+    testing.expect(mem.eql(u8, objects[0], "obj1"));
+    testing.expect(mem.eql(u8, objects[1], "obj2"));
 
-    debug.assert(mem.eql(u8, args.single("library").?, "lib2"));
+    testing.expect(mem.eql(u8, args.single("library").?, "lib2"));
 
     const pos = args.positionals.toSliceConst();
-    debug.assert(mem.eql(u8, pos[0], "build"));
-    debug.assert(mem.eql(u8, pos[1], "pos1"));
-    debug.assert(mem.eql(u8, pos[2], "pos2"));
+    testing.expect(mem.eql(u8, pos[0], "build"));
+    testing.expect(mem.eql(u8, pos[1], "pos1"));
+    testing.expect(mem.eql(u8, pos[2], "pos2"));
 }