Spring Boot + Thymeleaf (+gradle) で htmlファイルが表示されない

Spring Boot + thymelaefで最小構成で動かそうとしていますが、うまくいかないので質問を投稿いたします。

前提

OS: Windows 10
IDE: Intellij IDEA
Java11
- `>java --version

openjdk 11.0.2 2019-01-15
OpenJDK Runtime Environment 18.9 (build 11.0.2+9)
OpenJDK 64-Bit Server VM 18.9 (build 11.0.2+9, mixed mode)
`

Project SDKも同様にJDK11

ファイル構成

src\main\java\com\hoge\practice\spring\demo\controller\SampleController.java
src\main\java\com\hoge\practice\spring\demo\DemoApplication.java
src\main\resources\templates\test.html
src\main\resources\application.yml
build.gradle

ソースファイル内容

それぞれのファイルの内容は以下です。

SampleController.java

java
1package com.hoge.practice.spring.demo.controller;
2
3import org.springframework.stereotype.Controller;
4import org.springframework.ui.Model;
5import org.springframework.web.bind.annotation.GetMapping;
6import org.springframework.web.bind.annotation.RequestMapping;
7
8@Controller
9@RequestMapping(value = "/sample")
10public class SampleController {
11
12    @GetMapping("/test")
13    public String test(Model model){
14        model.addAttribute("title", "タイトル");
15        return "test";
16    }
17}

DemoApplication.java

java
1package com.hoge.practice.spring.demo;
2
3import org.springframework.boot.SpringApplication;
4import org.springframework.boot.autoconfigure.SpringBootApplication;
5
6@SpringBootApplication
7public class DemoApplication {
8
9    public static void main(String[] args) {
10        SpringApplication.run(DemoApplication.class, args);
11    }
12}
13

test.html

html
1<!DOCTYPE html>
2<html xmlns:th="http://www.thymeleaf.org">
3<head>
4    <meta charset="UTF-8" />
5    <title th:text="${title}">Insert title here</title>
6</head>
7<body>
8<h1 th:text="${title}">title</h1>
9<p> this is a sample page </p>
10</body>
11</html>

application.ymlは空

build.gradle

plugins {
    id 'org.springframework.boot' version '2.2.2.RELEASE'
    id 'io.spring.dependency-management' version '1.0.8.RELEASE'
    id 'java'
}

group = 'com.hoge.practice.spring.demo'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '11'

configurations {
    developmentOnly
    runtimeClasspath {
        extendsFrom developmentOnly
    }
    compileOnly {
        extendsFrom annotationProcessor
    }
}

repositories {
    mavenCentral()
}

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-jdbc'
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'org.springframework.boot:spring-boot-starter-thymeleaf'
    implementation 'org.springframework.boot:spring-boot-starter-validation'
    compileOnly 'org.projectlombok:lombok'
    developmentOnly 'org.springframework.boot:spring-boot-devtools'
    runtimeOnly 'com.h2database:h2'
    annotationProcessor 'org.springframework.boot:spring-boot-configuration-processor'
    annotationProcessor 'org.projectlombok:lombok'
    testImplementation('org.springframework.boot:spring-boot-starter-test') {
        exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
    }
}

test {
    useJUnitPlatform()
}

エラー内容

この状態で、 http://localhost:8080/sample/test にアクセスすると、Whitelabel Error Pageが表示されます。
コンソールのエラーの抜粋は以下です。

2020-01-09 22:37:54.229 ERROR 12060 --- [nio-8080-exec-1] org.thymeleaf.TemplateEngine             : [THYMELEAF][http-nio-8080-exec-1] Exception processing template "test": Error resolving template [test], template might not exist or might not be accessible by any of the configured Template Resolvers

org.thymeleaf.exceptions.TemplateInputException: Error resolving template [test], template might not exist or might not be accessible by any of the configured Template Resolvers
	at org.thymeleaf.engine.TemplateManager.resolveTemplate(TemplateManager.java:869) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]

(中略)

2020-01-09 22:37:54.233 ERROR 12060 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.thymeleaf.exceptions.TemplateInputException: Error resolving template [test], template might not exist or might not be accessible by any of the configured Template Resolvers] with root cause

org.thymeleaf.exceptions.TemplateInputException: Error resolving template [test], template might not exist or might not be accessible by any of the configured Template Resolvers
	at org.thymeleaf.engine.TemplateManager.resolveTemplate(TemplateManager.java:869) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]

また、気になる情報として、起動時のログに以下の警告が出ていました。

2020-01-09 22:37:50.172  WARN 12060 --- [  restartedMain] ion$DefaultTemplateResolverConfiguration : Cannot find template location: classpath:/templates/ (please add some templates or check your Thymeleaf configuration)

また、ページを開いた際、コントローラーの処理は通っています。