diff --git a/test_suite/tests/test_annotations.rs b/test_suite/tests/test_annotations.rs
index 9d03280d..b26ec872 100644
--- a/test_suite/tests/test_annotations.rs
+++ b/test_suite/tests/test_annotations.rs
@@ -1895,18 +1895,6 @@ fn test_expecting_message_externally_tagged_enum() {
     );
 }
 
-#[test]
-fn test_expecting_message_untagged_tagged_enum() {
-    #[derive(Deserialize)]
-    #[serde(untagged)]
-    #[serde(expecting = "something strange...")]
-    enum Enum {
-        Untagged,
-    }
-
-    assert_de_tokens_error::<Enum>(&[Token::Str("Untagged")], "something strange...");
-}
-
 #[test]
 fn test_expecting_message_identifier_enum() {
     #[derive(Deserialize)]
@@ -2958,41 +2946,6 @@ mod flatten {
         mod untagged {
             use super::*;
 
-            #[test]
-            fn straightforward() {
-                #[derive(Serialize, Deserialize, PartialEq, Debug)]
-                #[serde(untagged)]
-                enum Data {
-                    A {
-                        a: i32,
-                        #[serde(flatten)]
-                        flat: Flat,
-                    },
-                }
-
-                #[derive(Serialize, Deserialize, PartialEq, Debug)]
-                struct Flat {
-                    b: i32,
-                }
-
-                let data = Data::A {
-                    a: 0,
-                    flat: Flat { b: 0 },
-                };
-
-                assert_tokens(
-                    &data,
-                    &[
-                        Token::Map { len: None },
-                        Token::Str("a"),
-                        Token::I32(0),
-                        Token::Str("b"),
-                        Token::I32(0),
-                        Token::MapEnd,
-                    ],
-                );
-            }
-
             #[derive(Debug, PartialEq, Serialize, Deserialize)]
             struct Flatten {
                 #[serde(flatten)]
diff --git a/test_suite/tests/test_enum_untagged.rs b/test_suite/tests/test_enum_untagged.rs
new file mode 100644
index 00000000..1c7ce542
--- /dev/null
+++ b/test_suite/tests/test_enum_untagged.rs
@@ -0,0 +1,409 @@
+#![deny(trivial_numeric_casts)]
+#![allow(
+    clippy::derive_partial_eq_without_eq,
+    clippy::enum_variant_names,
+    clippy::redundant_field_names,
+    clippy::too_many_lines
+)]
+
+mod bytes;
+
+use serde_derive::{Deserialize, Serialize};
+use serde_test::{assert_de_tokens, assert_de_tokens_error, assert_tokens, Token};
+use std::collections::BTreeMap;
+
+#[test]
+fn complex() {
+    #[derive(Debug, PartialEq, Serialize, Deserialize)]
+    #[serde(untagged)]
+    enum Untagged {
+        A { a: u8 },
+        B { b: u8 },
+        C,
+        D(u8),
+        E(String),
+        F(u8, u8),
+    }
+
+    assert_tokens(
+        &Untagged::A { a: 1 },
+        &[
+            Token::Struct {
+                name: "Untagged",
+                len: 1,
+            },
+            Token::Str("a"),
+            Token::U8(1),
+            Token::StructEnd,
+        ],
+    );
+
+    assert_tokens(
+        &Untagged::B { b: 2 },
+        &[
+            Token::Struct {
+                name: "Untagged",
+                len: 1,
+            },
+            Token::Str("b"),
+            Token::U8(2),
+            Token::StructEnd,
+        ],
+    );
+
+    // Serializes to unit, deserializes from either depending on format's
+    // preference.
+    assert_tokens(&Untagged::C, &[Token::Unit]);
+    assert_de_tokens(&Untagged::C, &[Token::None]);
+
+    assert_tokens(&Untagged::D(4), &[Token::U8(4)]);
+    assert_tokens(&Untagged::E("e".to_owned()), &[Token::Str("e")]);
+
+    assert_tokens(
+        &Untagged::F(1, 2),
+        &[
+            Token::Tuple { len: 2 },
+            Token::U8(1),
+            Token::U8(2),
+            Token::TupleEnd,
+        ],
+    );
+
+    assert_de_tokens_error::<Untagged>(
+        &[Token::Tuple { len: 1 }, Token::U8(1), Token::TupleEnd],
+        "data did not match any variant of untagged enum Untagged",
+    );
+
+    assert_de_tokens_error::<Untagged>(
+        &[
+            Token::Tuple { len: 3 },
+            Token::U8(1),
+            Token::U8(2),
+            Token::U8(3),
+            Token::TupleEnd,
+        ],
+        "data did not match any variant of untagged enum Untagged",
+    );
+}
+
+#[test]
+fn newtype_unit_and_empty_map() {
+    #[derive(Debug, PartialEq, Serialize, Deserialize)]
+    struct Unit;
+
+    #[derive(Debug, PartialEq, Serialize, Deserialize)]
+    #[serde(untagged)]
+    enum Message {
+        Unit(Unit),
+        Map(BTreeMap<String, String>),
+    }
+
+    assert_tokens(
+        &Message::Map(BTreeMap::new()),
+        &[Token::Map { len: Some(0) }, Token::MapEnd],
+    );
+}
+
+#[test]
+fn newtype_struct() {
+    #[derive(Debug, PartialEq, Serialize, Deserialize)]
+    struct GenericNewTypeStruct<T>(T);
+
+    #[derive(Debug, PartialEq, Serialize, Deserialize)]
+    #[serde(untagged)]
+    enum E {
+        Newtype(GenericNewTypeStruct<u32>),
+        Null,
+    }
+
+    assert_tokens(
+        &E::Newtype(GenericNewTypeStruct(5u32)),
+        &[
+            Token::NewtypeStruct {
+                name: "GenericNewTypeStruct",
+            },
+            Token::U32(5),
+        ],
+    );
+}
+
+#[test]
+fn newtype_enum() {
+    #[derive(Debug, PartialEq, Serialize, Deserialize)]
+    #[serde(untagged)]
+    enum Outer {
+        Inner(Inner),
+    }
+
+    #[derive(Debug, PartialEq, Serialize, Deserialize)]
+    enum Inner {
+        Unit,
+        Newtype(u8),
+        Tuple(u8, u8),
+        Struct { f: u8 },
+    }
+
+    assert_tokens(
+        &Outer::Inner(Inner::Unit),
+        &[Token::UnitVariant {
+            name: "Inner",
+            variant: "Unit",
+        }],
+    );
+
+    assert_tokens(
+        &Outer::Inner(Inner::Newtype(1)),
+        &[
+            Token::NewtypeVariant {
+                name: "Inner",
+                variant: "Newtype",
+            },
+            Token::U8(1),
+        ],
+    );
+
+    assert_tokens(
+        &Outer::Inner(Inner::Tuple(1, 1)),
+        &[
+            Token::TupleVariant {
+                name: "Inner",
+                variant: "Tuple",
+                len: 2,
+            },
+            Token::U8(1),
+            Token::U8(1),
+            Token::TupleVariantEnd,
+        ],
+    );
+
+    assert_tokens(
+        &Outer::Inner(Inner::Struct { f: 1 }),
+        &[
+            Token::StructVariant {
+                name: "Inner",
+                variant: "Struct",
+                len: 1,
+            },
+            Token::Str("f"),
+            Token::U8(1),
+            Token::StructVariantEnd,
+        ],
+    );
+}
+
+#[test]
+fn string_and_bytes() {
+    #[derive(Debug, PartialEq, Deserialize)]
+    #[serde(untagged)]
+    enum Untagged {
+        String {
+            string: String,
+        },
+        Bytes {
+            #[serde(with = "bytes")]
+            bytes: Vec<u8>,
+        },
+    }
+
+    assert_de_tokens(
+        &Untagged::String {
+            string: "\0".to_owned(),
+        },
+        &[
+            Token::Struct {
+                name: "Untagged",
+                len: 1,
+            },
+            Token::Str("string"),
+            Token::Str("\0"),
+            Token::StructEnd,
+        ],
+    );
+
+    assert_de_tokens(
+        &Untagged::String {
+            string: "\0".to_owned(),
+        },
+        &[
+            Token::Struct {
+                name: "Untagged",
+                len: 1,
+            },
+            Token::Str("string"),
+            Token::String("\0"),
+            Token::StructEnd,
+        ],
+    );
+
+    assert_de_tokens(
+        &Untagged::String {
+            string: "\0".to_owned(),
+        },
+        &[
+            Token::Struct {
+                name: "Untagged",
+                len: 1,
+            },
+            Token::Str("string"),
+            Token::Bytes(b"\0"),
+            Token::StructEnd,
+        ],
+    );
+
+    assert_de_tokens(
+        &Untagged::String {
+            string: "\0".to_owned(),
+        },
+        &[
+            Token::Struct {
+                name: "Untagged",
+                len: 1,
+            },
+            Token::Str("string"),
+            Token::ByteBuf(b"\0"),
+            Token::StructEnd,
+        ],
+    );
+
+    assert_de_tokens(
+        &Untagged::Bytes { bytes: vec![0] },
+        &[
+            Token::Struct {
+                name: "Untagged",
+                len: 1,
+            },
+            Token::Str("bytes"),
+            Token::Str("\0"),
+            Token::StructEnd,
+        ],
+    );
+
+    assert_de_tokens(
+        &Untagged::Bytes { bytes: vec![0] },
+        &[
+            Token::Struct {
+                name: "Untagged",
+                len: 1,
+            },
+            Token::Str("bytes"),
+            Token::String("\0"),
+            Token::StructEnd,
+        ],
+    );
+
+    assert_de_tokens(
+        &Untagged::Bytes { bytes: vec![0] },
+        &[
+            Token::Struct {
+                name: "Untagged",
+                len: 1,
+            },
+            Token::Str("bytes"),
+            Token::Bytes(b"\0"),
+            Token::StructEnd,
+        ],
+    );
+
+    assert_de_tokens(
+        &Untagged::Bytes { bytes: vec![0] },
+        &[
+            Token::Struct {
+                name: "Untagged",
+                len: 1,
+            },
+            Token::Str("bytes"),
+            Token::ByteBuf(b"\0"),
+            Token::StructEnd,
+        ],
+    );
+
+    assert_de_tokens(
+        &Untagged::Bytes { bytes: vec![0] },
+        &[
+            Token::Struct {
+                name: "Untagged",
+                len: 1,
+            },
+            Token::Str("bytes"),
+            Token::Seq { len: Some(1) },
+            Token::U8(0),
+            Token::SeqEnd,
+            Token::StructEnd,
+        ],
+    );
+}
+
+#[test]
+fn contains_flatten() {
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    #[serde(untagged)]
+    enum Data {
+        A {
+            a: i32,
+            #[serde(flatten)]
+            flat: Flat,
+        },
+    }
+
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    struct Flat {
+        b: i32,
+    }
+
+    let data = Data::A {
+        a: 0,
+        flat: Flat { b: 0 },
+    };
+
+    assert_tokens(
+        &data,
+        &[
+            Token::Map { len: None },
+            Token::Str("a"),
+            Token::I32(0),
+            Token::Str("b"),
+            Token::I32(0),
+            Token::MapEnd,
+        ],
+    );
+}
+
+#[test]
+fn contains_flatten_with_integer_key() {
+    #[derive(Debug, PartialEq, Serialize, Deserialize)]
+    #[serde(untagged)]
+    pub enum Untagged {
+        Variant {
+            #[serde(flatten)]
+            map: BTreeMap<u64, String>,
+        },
+    }
+
+    assert_tokens(
+        &Untagged::Variant {
+            map: {
+                let mut map = BTreeMap::new();
+                map.insert(100, "BTreeMap".to_owned());
+                map
+            },
+        },
+        &[
+            Token::Map { len: None },
+            Token::U64(100),
+            Token::Str("BTreeMap"),
+            Token::MapEnd,
+        ],
+    );
+}
+
+#[test]
+fn expecting_message() {
+    #[derive(Deserialize)]
+    #[serde(untagged)]
+    #[serde(expecting = "something strange...")]
+    enum Enum {
+        Untagged,
+    }
+
+    assert_de_tokens_error::<Enum>(&[Token::Str("Untagged")], "something strange...");
+}
diff --git a/test_suite/tests/test_macros.rs b/test_suite/tests/test_macros.rs
index aaab9581..6b2fc4c5 100644
--- a/test_suite/tests/test_macros.rs
+++ b/test_suite/tests/test_macros.rs
@@ -6,13 +6,8 @@
     clippy::too_many_lines
 )]
 
-mod bytes;
-
 use serde_derive::{Deserialize, Serialize};
-use serde_test::{
-    assert_de_tokens, assert_de_tokens_error, assert_ser_tokens, assert_tokens, Token,
-};
-use std::collections::BTreeMap;
+use serde_test::{assert_de_tokens, assert_ser_tokens, assert_tokens, Token};
 use std::marker::PhantomData;
 
 // That tests that the derived Serialize implementation doesn't trigger
@@ -433,26 +428,6 @@ fn test_generic_newtype_struct() {
     );
 }
 
-#[test]
-fn test_untagged_newtype_struct() {
-    #[derive(Debug, PartialEq, Serialize, Deserialize)]
-    #[serde(untagged)]
-    enum E {
-        Newtype(GenericNewTypeStruct<u32>),
-        Null,
-    }
-
-    assert_tokens(
-        &E::Newtype(GenericNewTypeStruct(5u32)),
-        &[
-            Token::NewtypeStruct {
-                name: "GenericNewTypeStruct",
-            },
-            Token::U32(5),
-        ],
-    );
-}
-
 #[test]
 fn test_generic_tuple_struct() {
     assert_tokens(
@@ -577,80 +552,6 @@ fn test_enum_state_field() {
     );
 }
 
-#[test]
-fn test_untagged_enum() {
-    #[derive(Debug, PartialEq, Serialize, Deserialize)]
-    #[serde(untagged)]
-    enum Untagged {
-        A { a: u8 },
-        B { b: u8 },
-        C,
-        D(u8),
-        E(String),
-        F(u8, u8),
-    }
-
-    assert_tokens(
-        &Untagged::A { a: 1 },
-        &[
-            Token::Struct {
-                name: "Untagged",
-                len: 1,
-            },
-            Token::Str("a"),
-            Token::U8(1),
-            Token::StructEnd,
-        ],
-    );
-
-    assert_tokens(
-        &Untagged::B { b: 2 },
-        &[
-            Token::Struct {
-                name: "Untagged",
-                len: 1,
-            },
-            Token::Str("b"),
-            Token::U8(2),
-            Token::StructEnd,
-        ],
-    );
-
-    // Serializes to unit, deserializes from either depending on format's
-    // preference.
-    assert_tokens(&Untagged::C, &[Token::Unit]);
-    assert_de_tokens(&Untagged::C, &[Token::None]);
-
-    assert_tokens(&Untagged::D(4), &[Token::U8(4)]);
-    assert_tokens(&Untagged::E("e".to_owned()), &[Token::Str("e")]);
-
-    assert_tokens(
-        &Untagged::F(1, 2),
-        &[
-            Token::Tuple { len: 2 },
-            Token::U8(1),
-            Token::U8(2),
-            Token::TupleEnd,
-        ],
-    );
-
-    assert_de_tokens_error::<Untagged>(
-        &[Token::Tuple { len: 1 }, Token::U8(1), Token::TupleEnd],
-        "data did not match any variant of untagged enum Untagged",
-    );
-
-    assert_de_tokens_error::<Untagged>(
-        &[
-            Token::Tuple { len: 3 },
-            Token::U8(1),
-            Token::U8(2),
-            Token::U8(3),
-            Token::TupleEnd,
-        ],
-        "data did not match any variant of untagged enum Untagged",
-    );
-}
-
 #[test]
 fn test_internally_tagged_struct() {
     #[derive(Debug, PartialEq, Serialize, Deserialize)]
@@ -750,240 +651,6 @@ fn test_internally_tagged_struct_with_flattened_field() {
     );
 }
 
-#[test]
-fn test_untagged_enum_with_flattened_integer_key() {
-    #[derive(Debug, PartialEq, Serialize, Deserialize)]
-    #[serde(untagged)]
-    pub enum Untagged {
-        Variant {
-            #[serde(flatten)]
-            map: BTreeMap<u64, String>,
-        },
-    }
-
-    assert_tokens(
-        &Untagged::Variant {
-            map: {
-                let mut map = BTreeMap::new();
-                map.insert(100, "BTreeMap".to_owned());
-                map
-            },
-        },
-        &[
-            Token::Map { len: None },
-            Token::U64(100),
-            Token::Str("BTreeMap"),
-            Token::MapEnd,
-        ],
-    );
-}
-
-#[test]
-fn test_enum_in_untagged_enum() {
-    #[derive(Debug, PartialEq, Serialize, Deserialize)]
-    #[serde(untagged)]
-    enum Outer {
-        Inner(Inner),
-    }
-
-    #[derive(Debug, PartialEq, Serialize, Deserialize)]
-    enum Inner {
-        Unit,
-        Newtype(u8),
-        Tuple(u8, u8),
-        Struct { f: u8 },
-    }
-
-    assert_tokens(
-        &Outer::Inner(Inner::Unit),
-        &[Token::UnitVariant {
-            name: "Inner",
-            variant: "Unit",
-        }],
-    );
-
-    assert_tokens(
-        &Outer::Inner(Inner::Newtype(1)),
-        &[
-            Token::NewtypeVariant {
-                name: "Inner",
-                variant: "Newtype",
-            },
-            Token::U8(1),
-        ],
-    );
-
-    assert_tokens(
-        &Outer::Inner(Inner::Tuple(1, 1)),
-        &[
-            Token::TupleVariant {
-                name: "Inner",
-                variant: "Tuple",
-                len: 2,
-            },
-            Token::U8(1),
-            Token::U8(1),
-            Token::TupleVariantEnd,
-        ],
-    );
-
-    assert_tokens(
-        &Outer::Inner(Inner::Struct { f: 1 }),
-        &[
-            Token::StructVariant {
-                name: "Inner",
-                variant: "Struct",
-                len: 1,
-            },
-            Token::Str("f"),
-            Token::U8(1),
-            Token::StructVariantEnd,
-        ],
-    );
-}
-
-#[test]
-fn test_untagged_bytes() {
-    #[derive(Debug, PartialEq, Deserialize)]
-    #[serde(untagged)]
-    enum Untagged {
-        String {
-            string: String,
-        },
-        Bytes {
-            #[serde(with = "bytes")]
-            bytes: Vec<u8>,
-        },
-    }
-
-    assert_de_tokens(
-        &Untagged::String {
-            string: "\0".to_owned(),
-        },
-        &[
-            Token::Struct {
-                name: "Untagged",
-                len: 1,
-            },
-            Token::Str("string"),
-            Token::Str("\0"),
-            Token::StructEnd,
-        ],
-    );
-
-    assert_de_tokens(
-        &Untagged::String {
-            string: "\0".to_owned(),
-        },
-        &[
-            Token::Struct {
-                name: "Untagged",
-                len: 1,
-            },
-            Token::Str("string"),
-            Token::String("\0"),
-            Token::StructEnd,
-        ],
-    );
-
-    assert_de_tokens(
-        &Untagged::String {
-            string: "\0".to_owned(),
-        },
-        &[
-            Token::Struct {
-                name: "Untagged",
-                len: 1,
-            },
-            Token::Str("string"),
-            Token::Bytes(b"\0"),
-            Token::StructEnd,
-        ],
-    );
-
-    assert_de_tokens(
-        &Untagged::String {
-            string: "\0".to_owned(),
-        },
-        &[
-            Token::Struct {
-                name: "Untagged",
-                len: 1,
-            },
-            Token::Str("string"),
-            Token::ByteBuf(b"\0"),
-            Token::StructEnd,
-        ],
-    );
-
-    assert_de_tokens(
-        &Untagged::Bytes { bytes: vec![0] },
-        &[
-            Token::Struct {
-                name: "Untagged",
-                len: 1,
-            },
-            Token::Str("bytes"),
-            Token::Str("\0"),
-            Token::StructEnd,
-        ],
-    );
-
-    assert_de_tokens(
-        &Untagged::Bytes { bytes: vec![0] },
-        &[
-            Token::Struct {
-                name: "Untagged",
-                len: 1,
-            },
-            Token::Str("bytes"),
-            Token::String("\0"),
-            Token::StructEnd,
-        ],
-    );
-
-    assert_de_tokens(
-        &Untagged::Bytes { bytes: vec![0] },
-        &[
-            Token::Struct {
-                name: "Untagged",
-                len: 1,
-            },
-            Token::Str("bytes"),
-            Token::Bytes(b"\0"),
-            Token::StructEnd,
-        ],
-    );
-
-    assert_de_tokens(
-        &Untagged::Bytes { bytes: vec![0] },
-        &[
-            Token::Struct {
-                name: "Untagged",
-                len: 1,
-            },
-            Token::Str("bytes"),
-            Token::ByteBuf(b"\0"),
-            Token::StructEnd,
-        ],
-    );
-
-    assert_de_tokens(
-        &Untagged::Bytes { bytes: vec![0] },
-        &[
-            Token::Struct {
-                name: "Untagged",
-                len: 1,
-            },
-            Token::Str("bytes"),
-            Token::Seq { len: Some(1) },
-            Token::U8(0),
-            Token::SeqEnd,
-            Token::StructEnd,
-        ],
-    );
-}
-
 #[test]
 fn test_rename_all() {
     #[derive(Serialize, Deserialize, Debug, PartialEq)]
@@ -1167,24 +834,6 @@ fn test_rename_all_fields() {
     );
 }
 
-#[test]
-fn test_untagged_newtype_variant_containing_unit_struct_not_map() {
-    #[derive(Debug, PartialEq, Serialize, Deserialize)]
-    struct Unit;
-
-    #[derive(Debug, PartialEq, Serialize, Deserialize)]
-    #[serde(untagged)]
-    enum Message {
-        Unit(Unit),
-        Map(BTreeMap<String, String>),
-    }
-
-    assert_tokens(
-        &Message::Map(BTreeMap::new()),
-        &[Token::Map { len: Some(0) }, Token::MapEnd],
-    );
-}
-
 #[test]
 fn test_packed_struct_can_derive_serialize() {
     #[derive(Copy, Clone, Serialize)]