test(derive): Rely on snapshot testing

`contains` assertions can be fairly brittle, easy to miss when wrong,
and hard to update.

Author: epage

tests/derive/app_name.rs

@@ -1,5 +1,8 @@
 use clap::CommandFactory;
 use clap::Parser;
+use snapbox::assert_data_eq;
+use snapbox::prelude::*;
+use snapbox::str;
 
 use crate::utils::get_help;
 use crate::utils::get_long_help;
@@ -12,7 +15,13 @@ fn app_name_in_short_help_from_struct() {
 
     let help = get_help::<MyApp>();
 
-    assert!(help.contains("my-cmd"));
+    assert_data_eq!(help, str![[r#"
+Usage: my-cmd
+
+Options:
+  -h, --help  Print help
+
+"#]].raw());
 }
 
 #[test]
@@ -23,7 +32,13 @@ fn app_name_in_long_help_from_struct() {
 
     let help = get_help::<MyApp>();
 
-    assert!(help.contains("my-cmd"));
+    assert_data_eq!(help, str![[r#"
+Usage: my-cmd
+
+Options:
+  -h, --help  Print help
+
+"#]].raw());
 }
 
 #[test]
@@ -34,7 +49,13 @@ fn app_name_in_short_help_from_enum() {
 
     let help = get_help::<MyApp>();
 
-    assert!(help.contains("my-cmd"));
+    assert_data_eq!(help, str![[r#"
+Usage: my-cmd
+
+Options:
+  -h, --help  Print help
+
+"#]].raw());
 }
 
 #[test]
@@ -45,7 +66,14 @@ fn app_name_in_long_help_from_enum() {
 
     let help = get_long_help::<MyApp>();
 
-    assert!(help.contains("my-cmd"));
+    assert_data_eq!(help, str![[r#"
+Usage: my-cmd
+
+Options:
+  -h, --help
+          Print help
+
+"#]].raw());
 }
 
 #[test]
@@ -56,7 +84,10 @@ fn app_name_in_short_version_from_struct() {
 
     let version = MyApp::command().render_version();
 
-    assert!(version.contains("my-cmd"));
+    assert_data_eq!(version, str![[r#"
+my-cmd 
+
+"#]].raw());
 }
 
 #[test]
@@ -67,7 +98,10 @@ fn app_name_in_long_version_from_struct() {
 
     let version = MyApp::command().render_long_version();
 
-    assert!(version.contains("my-cmd"));
+    assert_data_eq!(version, str![[r#"
+my-cmd 
+
+"#]].raw());
 }
 
 #[test]
@@ -78,7 +112,10 @@ fn app_name_in_short_version_from_enum() {
 
     let version = MyApp::command().render_version();
 
-    assert!(version.contains("my-cmd"));
+    assert_data_eq!(version, str![[r#"
+my-cmd 
+
+"#]].raw());
 }
 
 #[test]
@@ -89,5 +126,8 @@ fn app_name_in_long_version_from_enum() {
 
     let version = MyApp::command().render_long_version();
 
-    assert!(version.contains("my-cmd"));
+    assert_data_eq!(version, str![[r#"
+my-cmd 
+
+"#]].raw());
 }

tests/derive/arguments.rs

@@ -12,10 +12,13 @@
 // commit#ea76fa1b1b273e65e3b0b1046643715b49bec51f which is licensed under the
 // MIT/Apache 2.0 license.
 
-use clap::Parser;
-
 use crate::utils::get_help;
 
+use clap::Parser;
+use snapbox::assert_data_eq;
+use snapbox::prelude::*;
+use snapbox::str;
+
 #[test]
 fn required_argument() {
     #[derive(Parser, PartialEq, Debug)]
@@ -54,7 +57,17 @@ fn auto_value_name() {
 
     let help = get_help::<Opt>();
 
-    assert!(help.contains("MY_SPECIAL_ARG"));
+    assert_data_eq!(help, str![[r#"
+Usage: clap <MY_SPECIAL_ARG>
+
+Arguments:
+  <MY_SPECIAL_ARG>  
+
+Options:
+  -h, --help  Print help
+
+"#]].raw());
+
     // Ensure the implicit `num_vals` is just 1
     assert_eq!(
         Opt { my_special_arg: 10 },
@@ -72,8 +85,17 @@ fn explicit_value_name() {
 
     let help = get_help::<Opt>();
 
-    assert!(help.contains("BROWNIE_POINTS"));
-    assert!(!help.contains("MY_SPECIAL_ARG"));
+    assert_data_eq!(help, str![[r#"
+Usage: clap <BROWNIE_POINTS>
+
+Arguments:
+  <BROWNIE_POINTS>  
+
+Options:
+  -h, --help  Print help
+
+"#]].raw());
+
     // Ensure the implicit `num_vals` is just 1
     assert_eq!(
         Opt { my_special_arg: 10 },

tests/derive/author_version_about.rs

@@ -12,9 +12,12 @@
 // commit#ea76fa1b1b273e65e3b0b1046643715b49bec51f which is licensed under the
 // MIT/Apache 2.0 license.
 
-use crate::utils;
-
 use clap::Parser;
+use snapbox::assert_data_eq;
+use snapbox::prelude::*;
+use snapbox::str;
+
+use crate::utils;
 
 #[test]
 fn no_author_version_about() {
@@ -35,9 +38,20 @@ fn use_env() {
     struct Opt {}
 
     let output = utils::get_long_help::<Opt>();
-    assert!(output.starts_with("clap"));
-    assert!(output
-        .contains("A simple to use, efficient, and full-featured Command Line Argument Parser"));
+    assert_data_eq!(output, str![[r#"
+clap 4.5.43
+A simple to use, efficient, and full-featured Command Line Argument Parser
+
+Usage: clap
+
+Options:
+  -h, --help
+          Print help
+
+  -V, --version
+          Print version
+
+"#]].raw());
 }
 
 #[test]
@@ -50,5 +64,17 @@ fn explicit_version_not_str_lit() {
     pub(crate) struct Opt {}
 
     let output = utils::get_long_help::<Opt>();
-    assert!(output.contains("custom version"));
+    assert_data_eq!(output, str![[r#"
+clap custom version
+
+Usage: clap
+
+Options:
+  -h, --help
+          Print help
+
+  -V, --version
+          Print version
+
+"#]].raw());
 }

tests/derive/custom_string_parsers.rs

@@ -12,11 +12,14 @@
 // commit#ea76fa1b1b273e65e3b0b1046643715b49bec51f which is licensed under the
 // MIT/Apache 2.0 license.
 
-use clap::Parser;
-
 use std::num::ParseIntError;
 use std::path::PathBuf;
 
+use clap::Parser;
+use snapbox::assert_data_eq;
+use snapbox::prelude::*;
+use snapbox::str;
+
 #[derive(Parser, PartialEq, Debug)]
 struct PathOpt {
     #[arg(short, long)]
@@ -82,11 +85,12 @@ fn test_parse_hex() {
     );
 
     let err = HexOpt::try_parse_from(["test", "-n", "gg"]).unwrap_err();
-    assert!(
-        err.to_string().contains("invalid digit found in string"),
-        "{}",
-        err
-    );
+    assert_data_eq!(err.to_string(), str![[r#"
+error: invalid value 'gg' for '-n <NUMBER>': invalid digit found in string
+
+For more information, try '--help'.
+
+"#]].raw());
 }
 
 #[derive(Debug)]