I found some more passing behavior tests

test/behavior/usingnamespace.zig

@@ -1,4 +1,5 @@
 const std = @import("std");
+const expect = std.testing.expect;
 
 const A = struct {
     pub const B = bool;
@@ -11,3 +12,42 @@ const C = struct {
 test "basic usingnamespace" {
     try std.testing.expect(C.B == bool);
 }
+
+fn Foo(comptime T: type) type {
+    return struct {
+        usingnamespace T;
+    };
+}
+
+test "usingnamespace inside a generic struct" {
+    const std2 = Foo(std);
+    const testing2 = Foo(std.testing);
+    try std2.testing.expect(true);
+    try testing2.expect(true);
+}
+
+usingnamespace struct {
+    pub const foo = 42;
+};
+
+test "usingnamespace does not redeclare an imported variable" {
+    comptime try std.testing.expect(@This().foo == 42);
+}
+
+usingnamespace @import("usingnamespace/foo.zig");
+test "usingnamespace omits mixing in private functions" {
+    try expect(@This().privateFunction());
+    try expect(!@This().printText());
+}
+fn privateFunction() bool {
+    return true;
+}
+
+test {
+    _ = @import("usingnamespace/import_segregation.zig");
+}
+
+usingnamespace @import("usingnamespace/a.zig");
+test "two files usingnamespace import each other" {
+    try expect(@This().ok());
+}