start to make test runner aware of logging

by default the test runner will only print logs with "warning" or
higher. this can be configured via the std.testing API.

See #5738 for future plans

Author: andrewrk

lib/std/special/test_runner.zig

@@ -21,6 +21,7 @@ pub fn main() anyerror!void {
 
     for (test_fn_list) |test_fn, i| {
         std.testing.base_allocator_instance.reset();
+        std.testing.log_level = .warn;
 
         var test_node = root_node.start(test_fn.name, null);
         test_node.activate();
@@ -73,3 +74,14 @@ pub fn main() anyerror!void {
         std.debug.warn("{} passed; {} skipped.\n", .{ ok_count, skip_count });
     }
 }
+
+pub fn log(
+    comptime message_level: std.log.Level,
+    comptime scope: @Type(.EnumLiteral),
+    comptime format: []const u8,
+    args: var,
+) void {
+    if (@enumToInt(message_level) <= @enumToInt(std.testing.log_level)) {
+        std.debug.print("[{}] ({}): " ++ format, .{@tagName(scope), @tagName(message_level)} ++ args);
+    }
+}

lib/std/testing.zig

@@ -14,6 +14,9 @@ pub var failing_allocator_instance = FailingAllocator.init(&base_allocator_insta
 pub var base_allocator_instance = std.mem.validationWrap(std.heap.ThreadSafeFixedBufferAllocator.init(allocator_mem[0..]));
 var allocator_mem: [2 * 1024 * 1024]u8 = undefined;
 
+/// TODO https://github.com/ziglang/zig/issues/5738
+pub var log_level = std.log.Level.warn;
+
 /// This function is intended to be used only in tests. It prints diagnostics to stderr
 /// and then aborts when actual_error_union is not expected_error.
 pub fn expectError(expected_error: anyerror, actual_error_union: var) void {