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, 2 deletions

diff --git a/std/rb.zig b/std/rb.zig
index beb7f3aae9..27e60dca6a 100644
--- a/std/rb.zig
+++ b/std/rb.zig
@@ -1,5 +1,6 @@
 const std = @import("index.zig");
 const assert = std.debug.assert;
+const testing = std.testing;
 const mem = std.mem; // For mem.Compare
 
 const Color = enum(u1) {
@@ -533,13 +534,13 @@ test "rb" {
     _ = tree.insert(&ns[8].node);
     _ = tree.insert(&ns[9].node);
     tree.remove(&ns[3].node);
-    assert(tree.insert(&dup.node) == &ns[7].node);
+    testing.expect(tree.insert(&dup.node) == &ns[7].node);
     try tree.replace(&ns[7].node, &dup.node);
 
     var num: *testNumber = undefined;
     num = testGetNumber(tree.first().?);
     while (num.node.next() != null) {
-        assert(testGetNumber(num.node.next().?).value > num.value);
+        testing.expect(testGetNumber(num.node.next().?).value > num.value);
         num = testGetNumber(num.node.next().?);
     }
 }