migrate SystemTests

Author: tayloraswift

Package.swift

@@ -682,10 +682,9 @@ let package:Package = .init(
                 .target(name: "Symbols"),
             ]),
 
-        .executableTarget(name: "SystemTests",
+        .testTarget(name: "SystemTests",
             dependencies: [
                 .target(name: "System_"),
-                .target(name: "Testing_"),
             ],
             exclude: [
                 "directories",

Sources/SystemTests/Directories.swift

@@ -0,0 +1,90 @@
+import System_
+import Testing
+
+@Suite
+enum Directories
+{
+    @Test
+    static func ExistenceDoesNotExist() throws
+    {
+        let path:FilePath = "Sources/SystemTests/TheLimit"
+        #expect(!path.directory.exists())
+    }
+    @Test
+    static func ExistenceDoesExist() throws
+    {
+        let path:FilePath = "Sources/SystemTests/directories/flat"
+        #expect(path.directory.exists())
+    }
+    @Test
+    static func ExistenceIsSymlink() throws
+    {
+        let path:FilePath = "Sources/SystemTests/directories/flat-link/a.txt"
+        #expect(!path.directory.exists())
+    }
+    @Test
+    static func ExistenceIsSymlinkToDirectory() throws
+    {
+        let path:FilePath = "Sources/SystemTests/directories/flat-link"
+        #expect(path.directory.exists())
+    }
+    @Test
+    static func ExistenceIsNotDirectory() throws
+    {
+        let path:FilePath = "Sources/SystemTests/directories/flat/a.txt"
+        #expect(!path.directory.exists())
+    }
+    @Test
+    static func Flat() throws
+    {
+        var files:[FilePath] = []
+
+        let path:FilePath = "Sources/SystemTests/directories/flat"
+        try path.directory.walk
+        {
+            files.append($0)
+            return true
+        }
+        let discovered:Set<FilePath.Component> = files.reduce(into: [])
+        {
+            if  let file:FilePath.Component = $1.lastComponent
+            {
+                $0.insert(file)
+            }
+        }
+
+        #expect(discovered == ["a.txt", "b.txt", "c.txt"])
+    }
+
+    @Test
+    static func Complex() throws
+    {
+        var files:[FilePath] = []
+
+        let path:FilePath = "Sources/SystemTests/directories/complex"
+        try path.directory.walk
+        {
+            files.append($0)
+            return true
+        }
+
+        let discovered:Set<FilePath.Component> = files.reduce(into: [])
+        {
+            if  let file:FilePath.Component = $1.lastComponent
+            {
+                $0.insert(file)
+            }
+        }
+
+        #expect(discovered == [
+                "a.txt",
+                "b.txt",
+                "x",
+                    "c.txt",
+                    "y",
+                        "d.txt",
+                    "z",
+                        "e.txt"
+            ])
+    }
+}