Add CLI integration tests

Cargo.lock

@@ -20,6 +20,20 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "assert_cmd"
+version = "2.0.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9834fcc22e0874394a010230586367d4a3e9f11b560f469262678547e1d2575e"
+dependencies = [
+ "bstr",
+ "doc-comment",
+ "predicates",
+ "predicates-core",
+ "predicates-tree",
+ "wait-timeout",
+]
+
 [[package]]
 name = "atty"
 version = "0.2.14"
@@ -43,6 +57,18 @@ version = "1.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
 
+[[package]]
+name = "bstr"
+version = "1.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5ffdb39cb703212f3c11973452c2861b972f757b021158f3516ba10f2fa8b2c1"
+dependencies = [
+ "memchr",
+ "once_cell",
+ "regex-automata",
+ "serde",
+]
+
 [[package]]
 name = "bumpalo"
 version = "3.11.1"
@@ -199,10 +225,17 @@ version = "0.1.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0e25ea47919b1560c4e3b7fe0aaab9becf5b84a10325ddf7db0f0ba5e1026499"
 
+[[package]]
+name = "difflib"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6184e33543162437515c2e2b48714794e37845ec9851711914eec9d308f6ebe8"
+
 [[package]]
 name = "difftastic"
 version = "0.44.0"
 dependencies = [
+ "assert_cmd",
  "bumpalo",
  "cc",
  "clap",
@@ -231,6 +264,12 @@ dependencies = [
  "wu-diff",
 ]
 
+[[package]]
+name = "doc-comment"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fea41bba32d969b513997752735605054bc0dfa92b4c56bf1189f2e174be7a10"
+
 [[package]]
 name = "either"
 version = "1.6.1"
@@ -409,9 +448,9 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "1.12.0"
+version = "1.17.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7709cef83f0c1f58f666e746a08b21e0085f7440fa6a29cc194d68aac97a4225"
+checksum = "b7e5500299e16ebb147ae15a00a942af264cf3688f47923b8fc2cd5858f23ad3"
 
 [[package]]
 name = "os_str_bytes"
@@ -467,6 +506,33 @@ dependencies = [
  "indexmap",
 ]
 
+[[package]]
+name = "predicates"
+version = "2.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "59230a63c37f3e18569bdb90e4a89cbf5bf8b06fea0b84e65ea10cc4df47addd"
+dependencies = [
+ "difflib",
+ "itertools",
+ "predicates-core",
+]
+
+[[package]]
+name = "predicates-core"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72f883590242d3c6fc5bf50299011695fa6590c2c70eac95ee1bdb9a733ad1a2"
+
+[[package]]
+name = "predicates-tree"
+version = "1.0.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "54ff541861505aabf6ea722d2131ee980b8276e10a1297b94e896dd8b621850d"
+dependencies = [
+ "predicates-core",
+ "termtree",
+]
+
 [[package]]
 name = "pretty_assertions"
 version = "1.2.1"
@@ -561,6 +627,12 @@ dependencies = [
  "regex-syntax",
 ]
 
+[[package]]
+name = "regex-automata"
+version = "0.1.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6c230d73fb8d8c1b9c0b3135c5142a8acee3a0558fb8db5cf1cb65f8d7862132"
+
 [[package]]
 name = "regex-syntax"
 version = "0.6.26"
@@ -588,6 +660,12 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
 
+[[package]]
+name = "serde"
+version = "1.0.152"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bb7d1f0d3021d347a83e556fc4683dea2ea09d87bccdf88ff5c12545d89d5efb"
+
 [[package]]
 name = "signal-hook"
 version = "0.3.14"
@@ -660,6 +738,12 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "termtree"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "95059e91184749cb66be6dc994f67f182b6d897cb3df74a5bf66b5e709295fd8"
+
 [[package]]
 name = "textwrap"
 version = "0.15.0"
@@ -722,6 +806,15 @@ version = "0.9.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
 
+[[package]]
+name = "wait-timeout"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9f200f5b12eb75f8c1ed65abd4b2db8a6e1b138a20de009dacee265a2498f3f6"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "walkdir"
 version = "2.3.2"

Cargo.toml

@@ -56,6 +56,7 @@ crossterm = { version = "0.25.0", features = [] }
 
 [dev-dependencies]
 pretty_assertions = "1.2.1"
+assert_cmd = "2.0.8"
 
 [build-dependencies]
 cc = "1.0.78"

tests/cli.rs

@@ -0,0 +1,10 @@
+use assert_cmd::prelude::*;
+use std::process::Command;
+
+#[test]
+fn no_such_files() {
+    let mut cmd = Command::cargo_bin("difft").unwrap();
+
+    cmd.arg("no_such_file").arg("no_such_file_either");
+    cmd.assert().failure().code(2);
+}