feat: Moves core functionality into it's own library.

Tests/CliDocCoreTests/CliDocCoreTests.swift

@@ -0,0 +1,136 @@
+@testable import CliDocCore
+@preconcurrency import Rainbow
+import Testing
+
+@Suite("CliDocCore Tests")
+struct CliDocCoreTests {
+  // Ensure that rainbow is setup, for test comparisons to work properly.
+  let setupRainbow: Bool = {
+    Rainbow.enabled = true
+    Rainbow.outputTarget = .console
+    return true
+  }()
+
+  @Test
+  func testGroup() {
+    #expect(setupRainbow)
+    let group = Group {
+      "foo"
+      "bar"
+      if setupRainbow {
+        "baz".color(.blue)
+      }
+    }
+    #expect(group.render() == "foobar\("baz".blue)")
+  }
+
+  @Test
+  func testHStack() {
+    #expect(setupRainbow)
+    let stack = HStack {
+      "foo"
+      "bar"
+    }
+    #expect(stack.render() == "foo bar")
+  }
+
+  @Test
+  func testVStack() {
+    #expect(setupRainbow)
+    let stack = VStack {
+      "foo"
+      "bar"
+    }
+    #expect(stack.render() == """
+    foo
+    bar
+    """)
+  }
+
+  @Test
+  func testOptionalTextNode() {
+    let someNode = String?.some("string")
+    #expect(someNode.body.render() == "string")
+    #expect(someNode.render() == "string")
+
+    let noneNode = String?.none
+    #expect(noneNode.body.render() == "")
+    #expect(noneNode.render() == "")
+  }
+
+  @Test
+  func testArrayTextNode() {
+    let array = ["foo", " ", "bar"]
+    #expect(array.body.render() == "foo bar")
+    #expect(array.render() == "foo bar")
+  }
+
+  @Test(
+    arguments: SectionArg.arguments
+  )
+  func testSection(arg: SectionArg) {
+    #expect(setupRainbow)
+    printIfNotEqual(arg.section.render(), arg.expected)
+    #expect(arg.section.render() == arg.expected)
+  }
+
+  struct SectionArg: @unchecked Sendable {
+    let section: any TextNode
+    let expected: String
+
+    static var arguments: [Self] {
+      [
+        .init(
+          section: Section {
+            "Content"
+          } header: {
+            "Header"
+          } footer: {
+            "Footer"
+          },
+          expected: """
+          Header
+
+          Content
+
+          Footer
+          """
+        ),
+        .init(
+          section: Section {
+            "Content"
+          } footer: {
+            "Footer"
+          },
+          expected: """
+          Content
+
+          Footer
+          """
+        ),
+        .init(
+          section: Section {
+            "Content"
+          } header: {
+            "Header"
+          },
+          expected: """
+          Header
+
+          Content
+          """
+        )
+      ]
+    }
+  }
+}
+
+@discardableResult
+func printIfNotEqual(_ lhs: String, _ rhs: String) -> Bool {
+  guard lhs == rhs else {
+    print(lhs)
+    print(rhs)
+    return false
+  }
+  return true
+}