Some minor changes for the 'if' implementation

* Made the conditiion label optional (looks more like an if statement)
* Add basic tests to check that the condition is handled correctly

Author: dagronf

Sources/QRCode/QRCode+Builder.swift

@@ -180,17 +180,27 @@ public extension QRCode.Builder {
 // MARK: - If condition
 
 public extension QRCode.Builder {
-    /// Conditionally apply qr code style if a boolean is `true`, just like a regular `if` statement
-    ///  - Parameter condition: A condition that has to be `true`
-    ///  - Parameter configure: The `QRCode.Builder` modifier(s) that you want to apply if `condition == true`
-    ///  - Returns: `QRCode.Builder`
-    func `if`(condition: Bool, configure: (QRCode.Builder) -> Void) -> QRCode.Builder {
-        let builder = self
-        if condition {
-            configure(builder)
-        }
-        return builder
-    }
+	/// Conditionally apply qr code style if a boolean is `true`, just like a regular `if` statement
+	///  - Parameter condition: A condition that has to be `true` for the configure block to execute
+	///  - Parameter configureBlock: The `QRCode.Builder` modifier(s) that you want to apply if `condition == true`
+	///  - Returns: `QRCode.Builder`
+	///
+	/// Usage:
+	///
+	/// ```swift
+	/// let qrcodebuilder = try QRCode.build
+	///    .text("Sample QR-code")
+	///    .if(<some_condition>) { builder in
+	///        builder.background.cornerRadius(0.75)
+	///    }
+	/// ```
+	@discardableResult func `if`(_ condition: Bool, _ configureBlock: (QRCode.Builder) -> Void) -> QRCode.Builder {
+		let builder = self
+		if condition {
+			configureBlock(builder)
+		}
+		return builder
+	}
 }
 
 // MARK: - Foreground

Tests/QRCodeTests/QRCodeBuilderTests.swift

@@ -181,4 +181,30 @@ final class QRCodeBuilderTests: XCTestCase {
 			try outputFolder.write(image, to: "builder-generated-rotate2.svg")
 		}
 	}
+
+	func testIfConditionBuilding() throws {
+		do {
+			// Check that the block is NOT executed if the condition is false
+			let qr1 = try QRCode.build
+				.text("Fish and chips")
+				.errorCorrection(.low)
+				.if(false) { builder in
+					builder.errorCorrection(.high)
+				}
+				.document
+			XCTAssertEqual(qr1.errorCorrection, .low)
+		}
+		do {
+			// Check that the block is executed if the condition is true
+			let qr1 = try QRCode.build
+				.text("Fish and chips")
+				.errorCorrection(.low)
+				.if(true) { builder in
+					builder.errorCorrection(.high)
+				}
+				.document
+			XCTAssertEqual(qr1.errorCorrection, .high)
+		}
+	}
+
 }