函数定义在cpp文件中时链接器错误

我的解决方案有三个项目:GoogleTest(用于使用Google Test)，Vi(用于大部分逻辑)和ViTests(用于使用Vi的单元测试). ViTests项目引用了Vi项目和Google Test项目.

My solution has three projects: GoogleTest (for using Google Test), Vi (for the bulk of the logic) and ViTests (for the unit tests using Vi). The ViTests project references the Vi project and the Google Test project.

Vi在v1.h中具有以下代码

Vi has the following code in v1.h

#pragma once

namespace Vi
{
    class Vi1
    {
    public:
        int SomeInt();
    };
}

和匹配的v1.cpp

And the matching v1.cpp

#include "vi1.h"

namespace Vi
{
    int Vi1::SomeInt()
    {
        return 123;
    }
}

随后是ViTests中的测试功能

The test function in ViTests follows

TEST(Vi1Foo, SomeIntIsSame)
{
    Vi1 v = Vi1{};
    EXPECT_EQ(123, v.SomeInt());
}

链接器错误表明存在未解析的符号SomeInt.但是，我可以通过如下内联函数来使链接器错误消失:

The linker error says there's an unresolved symbol SomeInt. However, I can make the linker error go away by inlining the function like so:

namespace Vi
{
    class Vi1
    {
    public:
        int SomeInt() { return 123; }
    };
}

为什么单元测试项目放在单独的cpp文件中时找不到SomeInt函数定义?

Why is the unit test project not finding the SomeInt function definition when it's placed in a separate cpp file?

谢谢.

其他详细信息以防万一:我正在使用Visual Studio 2015.

Extra details incase useful: I'm using Visual Studio 2015.

错误消息:

Error   LNK2019 unresolved external symbol "public: int __thiscall Vi::Vi1::SomeInt(void)" (?SomeInt@Vi1@Vi@@QAEHXZ) referenced in function "private: virtual void __thiscall ViTests::Vi1Foo_SomeIntIsSame_Test::TestBody(void)" (?TestBody@Vi1Foo_SomeIntIsSame_Test@ViTests@@EAEXXZ) Vi_Tests    C:\Users\MyName\Vi\Vi_Tests\Vi_Tests.obj    1

项目类型: Vi是Win32应用程序，ViTests是Win32控制台应用程序，GoogleTest是静态库.

Project types: Vi is Win32 Application, ViTests is Win32 Console Application, GoogleTest is a static library.