Importing Swift code from Objective-C in a Test Target - It's Possible!

A.h

@interface A : NSObject
- (int)foo;
@end

A.m

#import "A.h"
#import "B.h"

@implementation A

- (int)foo {
    [B bar];
    return 1;
}

@end

ATest.m

#import <XCTest/XCTest.h>
#import "A.h"

@interface ATest : XCTestCase

@end

@implementation ATest

- (void)testFooReturns1 {
    A *a = [[A alloc] init];
    XCTAssertEqual([a foo], 1);
}

@end

B.h

@interface B : NSObject
+ (void)bar;
@end

B.m

#import "B.h"
#import "MyProject-Swift.h"

@implementation B

+ (void)bar {
    [C fooBar];
}

@end

C.swift

public class C: NSObject {
    public static func fooBar() -> Int {
        println("Swift code is running")
        return 3
    }
}

CTest.swift

import XCTest

class CTest: XCTestCase {

    func testFooBarReturns2() {
        XCTAssertEqual(C.fooBar(), 3)
    }

}