TestNG test not using TestPropertySource for injecting @Value

I'm trying to write tests for a class that has a field value injected from a properties file. I'm trying to utilize the TestPropertySource annotation to get values in there while running TestNG tests, but it seems to be ignoring my properties file.

There's dozens of similar questions, which I tried to carefully read and try their implementations where possible. It seems my question is yet slightly different though, here's why:

• "@TestPropertSource and @PropertySource don't work for JUnit": talks about JUnit instead of TestNG (might or might not be relevant?) and it also talks about injecting a property value into a field on the test class (as opposed to the unit under test).

• "@TestPropertySource not working?": talks about how to ignore missing properties, not how to fix it.

• "@TestPropertySource is not loading properties": also talks about injecting values in to test class fields (did try @RunWith or @SpringBootTest but that didn't help either).

• The other links in Google search results also didn't help.

What do you need to do to get a unit-under-test with @Value annotated fields set with their property? Can I somehow request spring to provide me with instances of my class instead of newing them myself?

Here's a minimal repro.

Foo.java

package nl.jeroenheijmans.stackoverflow.testngprops;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class Foo {
    @Value("${my.prop}")
    private String myProp;

    public String ExposeProp() {
        return myProp;
    }
}

FooTest.java

package nl.jeroenheijmans.stackoverflow.testngprops;

import org.springframework.test.context.TestPropertySource;
import org.testng.Assert;
import org.testng.annotations.Test;

@TestPropertySource("classpath:application.properties")
public class FooTest {
    @Test
    public void sanityCheck(){
        Foo foo = new Foo();
        Assert.assertNotNull(foo); // Success!
    }

    @Test
    public void testProperty() {
        Foo foo = new Foo();
        Assert.assertEquals(foo.ExposeProp(), "checkcheck"); // Fail!
    }
}

application.properties (in both the main and test folder)

my.prop=checkcheck

Main.java

package nl.jeroenheijmans.stackoverflow.testngprops;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.support.SpringBootServletInitializer;
import org.springframework.context.annotation.PropertySource;

@SpringBootApplication
@PropertySource(value = {"classpath:application.properties"})
public class Main extends SpringBootServletInitializer {
    public static void main(String... args) {
        SpringApplication.run(Main.class, args);
    }

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(Main.class);
    }
}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>nl.jeroenheijmans.stackoverflow</groupId>
    <artifactId>testngprops</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.mockito</groupId>
            <artifactId>mockito-all</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.testng</groupId>
            <artifactId>testng</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${org.springframework.boot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.testng</groupId>
                <artifactId>testng</artifactId>
                <version>${testng.version}</version>
                <scope>test</scope>
            </dependency>
            <dependency>
                <groupId>org.mockito</groupId>
                <artifactId>mockito-all</artifactId>
                <version>${mockito.version}</version>
                <scope>test</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>${maven.compiler.version}</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

    <properties>
        <java.version>1.8</java.version>
        <maven.compiler.version>3.5</maven.compiler.version>
        <org.springframework.boot.version>1.5.1.RELEASE</org.springframework.boot.version>
        <testng.version>6.9.10</testng.version>
        <mockito.version>1.9.5</mockito.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
</project>