diff --git a/tests/ui/box/empty-alloc-deref-rvalue.rs b/tests/ui/box/empty-alloc-deref-rvalue.rs
new file mode 100644
index 0000000000000..507a753467ac9
--- /dev/null
+++ b/tests/ui/box/empty-alloc-deref-rvalue.rs
@@ -0,0 +1,10 @@
+//! Smoke test: dereferencing boxed zero-sized types (ZSTs) should not crash.
+//!
+//! Originally a regression test of github.com/rust-lang/rust/issues/13360
+//! but repurposed for a smoke test.
+
+//@ run-pass
+
+pub fn main() {
+    let _: () = *Box::new(());
+}
diff --git a/tests/ui/exclusive-drop-and-copy.rs b/tests/ui/derives/copy-drop-mutually-exclusive.rs
similarity index 79%
rename from tests/ui/exclusive-drop-and-copy.rs
rename to tests/ui/derives/copy-drop-mutually-exclusive.rs
index 210ecaed7567d..5147605910d7b 100644
--- a/tests/ui/exclusive-drop-and-copy.rs
+++ b/tests/ui/derives/copy-drop-mutually-exclusive.rs
@@ -1,4 +1,4 @@
-// issue #20126
+//! Regression test for issue #20126: Copy and Drop traits are mutually exclusive
 
 #[derive(Copy, Clone)] //~ ERROR the trait `Copy` cannot be implemented
 struct Foo;
diff --git a/tests/ui/exclusive-drop-and-copy.stderr b/tests/ui/derives/copy-drop-mutually-exclusive.stderr
similarity index 83%
rename from tests/ui/exclusive-drop-and-copy.stderr
rename to tests/ui/derives/copy-drop-mutually-exclusive.stderr
index 340ca89c396b4..771bbc9256958 100644
--- a/tests/ui/exclusive-drop-and-copy.stderr
+++ b/tests/ui/derives/copy-drop-mutually-exclusive.stderr
@@ -1,11 +1,11 @@
 error[E0184]: the trait `Copy` cannot be implemented for this type; the type has a destructor
-  --> $DIR/exclusive-drop-and-copy.rs:3:10
+  --> $DIR/copy-drop-mutually-exclusive.rs:3:10
    |
 LL | #[derive(Copy, Clone)]
    |          ^^^^ `Copy` not allowed on types with destructors
 
 error[E0184]: the trait `Copy` cannot be implemented for this type; the type has a destructor
-  --> $DIR/exclusive-drop-and-copy.rs:10:10
+  --> $DIR/copy-drop-mutually-exclusive.rs:10:10
    |
 LL | #[derive(Copy, Clone)]
    |          ^^^^ `Copy` not allowed on types with destructors
diff --git a/tests/ui/empty-allocation-rvalue-non-null.rs b/tests/ui/empty-allocation-rvalue-non-null.rs
deleted file mode 100644
index 0cd4fde73eda8..0000000000000
--- a/tests/ui/empty-allocation-rvalue-non-null.rs
+++ /dev/null
@@ -1,7 +0,0 @@
-//@ run-pass
-
-#![allow(unused_variables)]
-
-pub fn main() {
-    let x: () = *Box::new(());
-}
diff --git a/tests/ui/empty-type-parameter-list.rs b/tests/ui/empty-type-parameter-list.rs
deleted file mode 100644
index e8d6b2a99640c..0000000000000
--- a/tests/ui/empty-type-parameter-list.rs
+++ /dev/null
@@ -1,24 +0,0 @@
-//@ run-pass
-// Test that empty type parameter list (<>) is synonymous with
-// no type parameters at all
-
-struct S<>;
-trait T<> {} //~ WARN trait `T` is never used
-enum E<> { V }
-impl<> T<> for S<> {}
-impl T for E {}
-fn foo<>() {}
-fn bar() {}
-
-fn main() {
-    let _ = S;
-    let _ = S::<>;
-    let _ = E::V;
-    let _ = E::<>::V;
-    foo();
-    foo::<>();
-
-    // Test that we can supply <> to non generic things
-    bar::<>();
-    let _: i32<>;
-}
diff --git a/tests/ui/error-should-say-copy-not-pod.rs b/tests/ui/error-should-say-copy-not-pod.rs
deleted file mode 100644
index 40c4730ef699b..0000000000000
--- a/tests/ui/error-should-say-copy-not-pod.rs
+++ /dev/null
@@ -1,7 +0,0 @@
-// Tests that the error message uses the word Copy, not Pod.
-
-fn check_bound<T:Copy>(_: T) {}
-
-fn main() {
-    check_bound("nocopy".to_string()); //~ ERROR : Copy` is not satisfied
-}
diff --git a/tests/ui/error-should-say-copy-not-pod.stderr b/tests/ui/error-should-say-copy-not-pod.stderr
deleted file mode 100644
index 6aa129fa29b53..0000000000000
--- a/tests/ui/error-should-say-copy-not-pod.stderr
+++ /dev/null
@@ -1,22 +0,0 @@
-error[E0277]: the trait bound `String: Copy` is not satisfied
-  --> $DIR/error-should-say-copy-not-pod.rs:6:17
-   |
-LL |     check_bound("nocopy".to_string());
-   |     ----------- ^^^^^^^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `String`
-   |     |
-   |     required by a bound introduced by this call
-   |
-note: required by a bound in `check_bound`
-  --> $DIR/error-should-say-copy-not-pod.rs:3:18
-   |
-LL | fn check_bound<T:Copy>(_: T) {}
-   |                  ^^^^ required by this bound in `check_bound`
-help: consider removing this method call, as the receiver has type `&'static str` and `&'static str: Copy` trivially holds
-   |
-LL -     check_bound("nocopy".to_string());
-LL +     check_bound("nocopy");
-   |
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/explicit-i-suffix.rs b/tests/ui/explicit-i-suffix.rs
deleted file mode 100644
index 0a6ed49ae2704..0000000000000
--- a/tests/ui/explicit-i-suffix.rs
+++ /dev/null
@@ -1,13 +0,0 @@
-//@ run-pass
-
-#![allow(unused_must_use)]
-
-pub fn main() {
-    let x: isize = 8;
-    let y = 9;
-    x + y;
-
-    let q: isize = -8;
-    let r = -9;
-    q + r;
-}
diff --git a/tests/ui/ext-nonexistent.rs b/tests/ui/ext-nonexistent.rs
deleted file mode 100644
index 1293324b67ebe..0000000000000
--- a/tests/ui/ext-nonexistent.rs
+++ /dev/null
@@ -1,2 +0,0 @@
-fn main() { iamnotanextensionthatexists!(""); }
-//~^ ERROR cannot find macro `iamnotanextensionthatexists` in this scope
diff --git a/tests/ui/ext-nonexistent.stderr b/tests/ui/ext-nonexistent.stderr
deleted file mode 100644
index edb59bba6e5d1..0000000000000
--- a/tests/ui/ext-nonexistent.stderr
+++ /dev/null
@@ -1,8 +0,0 @@
-error: cannot find macro `iamnotanextensionthatexists` in this scope
-  --> $DIR/ext-nonexistent.rs:1:13
-   |
-LL | fn main() { iamnotanextensionthatexists!(""); }
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 1 previous error
-
diff --git a/tests/ui/fact.rs b/tests/ui/fact.rs
deleted file mode 100644
index e94c12da01341..0000000000000
--- a/tests/ui/fact.rs
+++ /dev/null
@@ -1,26 +0,0 @@
-//@ run-pass
-
-fn f(x: isize) -> isize {
-    // println!("in f:");
-
-    println!("{}", x);
-    if x == 1 {
-        // println!("bottoming out");
-
-        return 1;
-    } else {
-        // println!("recurring");
-
-        let y: isize = x * f(x - 1);
-        // println!("returned");
-
-        println!("{}", y);
-        return y;
-    }
-}
-
-pub fn main() {
-    assert_eq!(f(5), 120);
-    // println!("all done");
-
-}
diff --git a/tests/ui/generics/empty-generic-brackets-equiv.rs b/tests/ui/generics/empty-generic-brackets-equiv.rs
new file mode 100644
index 0000000000000..d84498a60f80d
--- /dev/null
+++ b/tests/ui/generics/empty-generic-brackets-equiv.rs
@@ -0,0 +1,27 @@
+//! Test that empty type parameter list <> is equivalent to no type parameters
+//!
+//! Checks` that empty angle brackets <> are syntactically valid and equivalent
+//! to omitting type parameters entirely across various language constructs.
+
+//@ run-pass
+
+struct S<>;
+trait T<> {} //~ WARN trait `T` is never used
+enum E<> {
+    V
+}
+impl<> T<> for S<> {}
+impl T for E {}
+fn foo<>() {}
+fn bar() {}
+fn main() {
+    let _ = S;
+    let _ = S::<>;
+    let _ = E::V;
+    let _ = E::<>::V;
+    foo();
+    foo::<>();
+    // Test that we can supply <> to non-generic things
+    bar::<>();
+    let _: i32<>;
+}
diff --git a/tests/ui/empty-type-parameter-list.stderr b/tests/ui/generics/empty-generic-brackets-equiv.stderr
similarity index 76%
rename from tests/ui/empty-type-parameter-list.stderr
rename to tests/ui/generics/empty-generic-brackets-equiv.stderr
index 31a5015e99349..151ee4697b4ca 100644
--- a/tests/ui/empty-type-parameter-list.stderr
+++ b/tests/ui/generics/empty-generic-brackets-equiv.stderr
@@ -1,5 +1,5 @@
 warning: trait `T` is never used
-  --> $DIR/empty-type-parameter-list.rs:6:7
+  --> $DIR/empty-generic-brackets-equiv.rs:9:7
    |
 LL | trait T<> {}
    |       ^
diff --git a/tests/ui/ext-expand-inner-exprs.rs b/tests/ui/macros/nested-macro-expansion.rs
similarity index 71%
rename from tests/ui/ext-expand-inner-exprs.rs
rename to tests/ui/macros/nested-macro-expansion.rs
index 94610d0a328f0..3b94b1051c9b7 100644
--- a/tests/ui/ext-expand-inner-exprs.rs
+++ b/tests/ui/macros/nested-macro-expansion.rs
@@ -1,3 +1,5 @@
+//! Test nested macro expansion with concat! macros
+
 //@ run-pass
 
 static FOO : &'static str = concat!(concat!("hel", "lo"), "world");
diff --git a/tests/ui/resolve/nonexistent-macro.rs b/tests/ui/resolve/nonexistent-macro.rs
new file mode 100644
index 0000000000000..663075473a1c8
--- /dev/null
+++ b/tests/ui/resolve/nonexistent-macro.rs
@@ -0,0 +1,6 @@
+//! Test error handling for undefined macro calls
+
+fn main() {
+    iamnotanextensionthatexists!("");
+    //~^ ERROR cannot find macro `iamnotanextensionthatexists` in this scope
+}
diff --git a/tests/ui/resolve/nonexistent-macro.stderr b/tests/ui/resolve/nonexistent-macro.stderr
new file mode 100644
index 0000000000000..7e89e07bf30b8
--- /dev/null
+++ b/tests/ui/resolve/nonexistent-macro.stderr
@@ -0,0 +1,8 @@
+error: cannot find macro `iamnotanextensionthatexists` in this scope
+  --> $DIR/nonexistent-macro.rs:4:5
+   |
+LL |     iamnotanextensionthatexists!("");
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
diff --git a/tests/ui/auxiliary/pub-and-stability.rs b/tests/ui/stability-attribute/auxiliary/pub-and-stability.rs
similarity index 100%
rename from tests/ui/auxiliary/pub-and-stability.rs
rename to tests/ui/stability-attribute/auxiliary/pub-and-stability.rs
diff --git a/tests/ui/explore-issue-38412.rs b/tests/ui/stability-attribute/stability-privacy-interaction.rs
similarity index 64%
rename from tests/ui/explore-issue-38412.rs
rename to tests/ui/stability-attribute/stability-privacy-interaction.rs
index 2008b120faae1..e02816ae1e739 100644
--- a/tests/ui/explore-issue-38412.rs
+++ b/tests/ui/stability-attribute/stability-privacy-interaction.rs
@@ -1,28 +1,39 @@
+//! Regression test for issue #38412: interaction between stability attributes and privacy
+//!
+//! Tests that the compiler correctly handles the interaction between feature gates
+//! and privacy/visibility rules. Specifically verifies that enabled unstable features
+//! are accessible while disabled ones are properly rejected.
+
 //@ aux-build:pub-and-stability.rs
 
-// A big point of this test is that we *enable* `unstable_declared`,
-// but do *not* enable `unstable_undeclared`. This way we can check
-// that the compiler is letting in uses of enabled feature-gated
-// stuff but still rejecting uses of disabled feature-gated stuff.
+// Enable `unstable_declared` but not `unstable_undeclared` to test
+// that the compiler allows enabled features but rejects disabled ones
 #![feature(unstable_declared)]
 
 extern crate pub_and_stability;
 use pub_and_stability::{Record, Trait, Tuple};
 
 fn main() {
-    // Okay
+    // Test struct field access patterns
     let Record { .. } = Record::new();
 
-    // Okay
-    let Record { a_stable_pub: _, a_unstable_declared_pub: _, .. } = Record::new();
+    let Record {
+        a_stable_pub: _,
+        a_unstable_declared_pub: _,
+        ..
+    } = Record::new();
 
-    let Record { a_stable_pub: _, a_unstable_declared_pub: _, a_unstable_undeclared_pub: _, .. } =
-        Record::new();
-    //~^^ ERROR use of unstable library feature `unstable_undeclared`
+    let Record {
+        a_stable_pub: _,
+        a_unstable_declared_pub: _,
+        a_unstable_undeclared_pub: _,  //~ ERROR use of unstable library feature `unstable_undeclared`
+        ..
+    } = Record::new();
 
     let r = Record::new();
     let t = Tuple::new();
 
+    // Test field access with different stability/privacy combinations
     r.a_stable_pub;
     r.a_unstable_declared_pub;
     r.a_unstable_undeclared_pub; //~ ERROR use of unstable library feature
@@ -37,10 +48,12 @@ fn main() {
     t.4;                         //~ ERROR is private
     t.5;                         //~ ERROR is private
 
+    // Test trait method access
     r.stable_trait_method();
     r.unstable_declared_trait_method();
     r.unstable_undeclared_trait_method(); //~ ERROR use of unstable library feature
 
+    // Test inherent method access
     r.stable();
     r.unstable_declared();
     r.unstable_undeclared();              //~ ERROR use of unstable library feature
@@ -49,6 +62,7 @@ fn main() {
     r.pub_mod();                          //~ ERROR `pub_mod` is private
     r.private();                          //~ ERROR `private` is private
 
+    // Repeat tests for tuple struct
     let t = Tuple::new();
     t.stable_trait_method();
     t.unstable_declared_trait_method();
diff --git a/tests/ui/explore-issue-38412.stderr b/tests/ui/stability-attribute/stability-privacy-interaction.stderr
similarity index 84%
rename from tests/ui/explore-issue-38412.stderr
rename to tests/ui/stability-attribute/stability-privacy-interaction.stderr
index fca5c738d2769..991b3dbe0191b 100644
--- a/tests/ui/explore-issue-38412.stderr
+++ b/tests/ui/stability-attribute/stability-privacy-interaction.stderr
@@ -1,15 +1,15 @@
 error[E0658]: use of unstable library feature `unstable_undeclared`
-  --> $DIR/explore-issue-38412.rs:19:63
+  --> $DIR/stability-privacy-interaction.rs:29:9
    |
-LL |     let Record { a_stable_pub: _, a_unstable_declared_pub: _, a_unstable_undeclared_pub: _, .. } =
-   |                                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |         a_unstable_undeclared_pub: _,
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: see issue #38412 <https://github.com/rust-lang/rust/issues/38412> for more information
    = help: add `#![feature(unstable_undeclared)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0658]: use of unstable library feature `unstable_undeclared`
-  --> $DIR/explore-issue-38412.rs:28:5
+  --> $DIR/stability-privacy-interaction.rs:39:5
    |
 LL |     r.a_unstable_undeclared_pub;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -19,25 +19,25 @@ LL |     r.a_unstable_undeclared_pub;
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0616]: field `b_crate` of struct `Record` is private
-  --> $DIR/explore-issue-38412.rs:29:7
+  --> $DIR/stability-privacy-interaction.rs:40:7
    |
 LL |     r.b_crate;
    |       ^^^^^^^ private field
 
 error[E0616]: field `c_mod` of struct `Record` is private
-  --> $DIR/explore-issue-38412.rs:30:7
+  --> $DIR/stability-privacy-interaction.rs:41:7
    |
 LL |     r.c_mod;
    |       ^^^^^ private field
 
 error[E0616]: field `d_priv` of struct `Record` is private
-  --> $DIR/explore-issue-38412.rs:31:7
+  --> $DIR/stability-privacy-interaction.rs:42:7
    |
 LL |     r.d_priv;
    |       ^^^^^^ private field
 
 error[E0658]: use of unstable library feature `unstable_undeclared`
-  --> $DIR/explore-issue-38412.rs:35:5
+  --> $DIR/stability-privacy-interaction.rs:46:5
    |
 LL |     t.2;
    |     ^^^
@@ -47,25 +47,25 @@ LL |     t.2;
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0616]: field `3` of struct `pub_and_stability::Tuple` is private
-  --> $DIR/explore-issue-38412.rs:36:7
+  --> $DIR/stability-privacy-interaction.rs:47:7
    |
 LL |     t.3;
    |       ^ private field
 
 error[E0616]: field `4` of struct `pub_and_stability::Tuple` is private
-  --> $DIR/explore-issue-38412.rs:37:7
+  --> $DIR/stability-privacy-interaction.rs:48:7
    |
 LL |     t.4;
    |       ^ private field
 
 error[E0616]: field `5` of struct `pub_and_stability::Tuple` is private
-  --> $DIR/explore-issue-38412.rs:38:7
+  --> $DIR/stability-privacy-interaction.rs:49:7
    |
 LL |     t.5;
    |       ^ private field
 
 error[E0658]: use of unstable library feature `unstable_undeclared`
-  --> $DIR/explore-issue-38412.rs:42:7
+  --> $DIR/stability-privacy-interaction.rs:54:7
    |
 LL |     r.unstable_undeclared_trait_method();
    |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -75,7 +75,7 @@ LL |     r.unstable_undeclared_trait_method();
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0658]: use of unstable library feature `unstable_undeclared`
-  --> $DIR/explore-issue-38412.rs:46:7
+  --> $DIR/stability-privacy-interaction.rs:59:7
    |
 LL |     r.unstable_undeclared();
    |       ^^^^^^^^^^^^^^^^^^^
@@ -85,7 +85,7 @@ LL |     r.unstable_undeclared();
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0624]: method `pub_crate` is private
-  --> $DIR/explore-issue-38412.rs:48:7
+  --> $DIR/stability-privacy-interaction.rs:61:7
    |
 LL |     r.pub_crate();
    |       ^^^^^^^^^ private method
@@ -96,7 +96,7 @@ LL |         pub(crate) fn pub_crate(&self) -> i32 { self.d_priv }
    |         ------------------------------------- private method defined here
 
 error[E0624]: method `pub_mod` is private
-  --> $DIR/explore-issue-38412.rs:49:7
+  --> $DIR/stability-privacy-interaction.rs:62:7
    |
 LL |     r.pub_mod();
    |       ^^^^^^^ private method
@@ -107,7 +107,7 @@ LL |         pub(in crate::m) fn pub_mod(&self) -> i32 { self.d_priv }
    |         ----------------------------------------- private method defined here
 
 error[E0624]: method `private` is private
-  --> $DIR/explore-issue-38412.rs:50:7
+  --> $DIR/stability-privacy-interaction.rs:63:7
    |
 LL |     r.private();
    |       ^^^^^^^ private method
@@ -118,7 +118,7 @@ LL |         fn private(&self) -> i32 { self.d_priv }
    |         ------------------------ private method defined here
 
 error[E0658]: use of unstable library feature `unstable_undeclared`
-  --> $DIR/explore-issue-38412.rs:55:7
+  --> $DIR/stability-privacy-interaction.rs:69:7
    |
 LL |     t.unstable_undeclared_trait_method();
    |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -128,7 +128,7 @@ LL |     t.unstable_undeclared_trait_method();
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0658]: use of unstable library feature `unstable_undeclared`
-  --> $DIR/explore-issue-38412.rs:59:7
+  --> $DIR/stability-privacy-interaction.rs:73:7
    |
 LL |     t.unstable_undeclared();
    |       ^^^^^^^^^^^^^^^^^^^
@@ -138,7 +138,7 @@ LL |     t.unstable_undeclared();
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0624]: method `pub_crate` is private
-  --> $DIR/explore-issue-38412.rs:61:7
+  --> $DIR/stability-privacy-interaction.rs:75:7
    |
 LL |     t.pub_crate();
    |       ^^^^^^^^^ private method
@@ -149,7 +149,7 @@ LL |         pub(crate) fn pub_crate(&self) -> i32 { self.0 }
    |         ------------------------------------- private method defined here
 
 error[E0624]: method `pub_mod` is private
-  --> $DIR/explore-issue-38412.rs:62:7
+  --> $DIR/stability-privacy-interaction.rs:76:7
    |
 LL |     t.pub_mod();
    |       ^^^^^^^ private method
@@ -160,7 +160,7 @@ LL |         pub(in crate::m) fn pub_mod(&self) -> i32 { self.0 }
    |         ----------------------------------------- private method defined here
 
 error[E0624]: method `private` is private
-  --> $DIR/explore-issue-38412.rs:63:7
+  --> $DIR/stability-privacy-interaction.rs:77:7
    |
 LL |     t.private();
    |       ^^^^^^^ private method