diff --git a/build-all.sh b/build-all.sh
index 37ea9a1..e6a15d8 100755
--- a/build-all.sh
+++ b/build-all.sh
@@ -86,6 +86,7 @@ if [[ "$MODULE" == "module5" ]]
 then
   # ADD NEW MODULES HERE
   # (add new modules above the rest so you get quicker feedback if it fails)
+  build_gradle_module "spring-boot/spring-boot-mocking-modules"
   build_gradle_module "spring-boot/specification"
   build_gradle_module "spring-boot/hibernate-search"
   build_maven_module "core-java/streams/fileswithstreams"
diff --git a/spring-boot/spring-boot-mocking-modules/build.gradle b/spring-boot/spring-boot-mocking-modules/build.gradle
new file mode 100644
index 0000000..2942c53
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/build.gradle
@@ -0,0 +1,23 @@
+plugins {
+	id 'org.springframework.boot' version '2.4.0'
+	id 'io.spring.dependency-management' version '1.0.10.RELEASE'
+	id 'java'
+}
+
+group = 'io.reflectoring.modules'
+version = '0.0.1-SNAPSHOT'
+sourceCompatibility = '11'
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation 'org.springframework.boot:spring-boot-starter'
+	implementation 'org.springframework.boot:spring-boot-starter-web'
+	testImplementation 'org.springframework.boot:spring-boot-starter-test'
+}
+
+test {
+	useJUnitPlatform()
+}
diff --git a/spring-boot/spring-boot-mocking-modules/gradlew b/spring-boot/spring-boot-mocking-modules/gradlew
new file mode 100644
index 0000000..4f906e0
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/gradlew
@@ -0,0 +1,185 @@
+#!/usr/bin/env sh
+
+#
+# Copyright 2015 the original author or authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if [ "$cygwin" = "true" -o "$msys" = "true" ] ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=`expr $i + 1`
+    done
+    case $i in
+        0) set -- ;;
+        1) set -- "$args0" ;;
+        2) set -- "$args0" "$args1" ;;
+        3) set -- "$args0" "$args1" "$args2" ;;
+        4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Escape application args
+save () {
+    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+    echo " "
+}
+APP_ARGS=`save "$@"`
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+exec "$JAVACMD" "$@"
diff --git a/spring-boot/spring-boot-mocking-modules/gradlew.bat b/spring-boot/spring-boot-mocking-modules/gradlew.bat
new file mode 100644
index 0000000..107acd3
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/gradlew.bat
@@ -0,0 +1,89 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega
diff --git a/spring-boot/spring-boot-mocking-modules/settings.gradle b/spring-boot/spring-boot-mocking-modules/settings.gradle
new file mode 100644
index 0000000..36e88fe
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/settings.gradle
@@ -0,0 +1 @@
+rootProject.name = 'mocking-modules'
diff --git a/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/DemoApplication.java b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/DemoApplication.java
new file mode 100644
index 0000000..1809d31
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/DemoApplication.java
@@ -0,0 +1,15 @@
+package io.reflectoring.modules;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.annotation.ComponentScan;
+
+@SpringBootApplication
+@ComponentScan()
+public class DemoApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(DemoApplication.class, args);
+	}
+
+}
diff --git a/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/github/api/GitHubMutations.java b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/github/api/GitHubMutations.java
new file mode 100644
index 0000000..cb635ea
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/github/api/GitHubMutations.java
@@ -0,0 +1,7 @@
+package io.reflectoring.modules.github.api;
+
+public interface GitHubMutations {
+
+    String createRepository(String token, GitHubRepository repository);
+
+}
diff --git a/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/github/api/GitHubQueries.java b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/github/api/GitHubQueries.java
new file mode 100644
index 0000000..4af78ba
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/github/api/GitHubQueries.java
@@ -0,0 +1,13 @@
+package io.reflectoring.modules.github.api;
+
+import java.util.List;
+
+public interface GitHubQueries {
+
+    List<String> getOrganisations(String token);
+
+    List<String> getRepositories(String token, String organisation);
+
+    boolean repositoryExists(String token, String repositoryName, String organisation);
+
+}
diff --git a/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/github/api/GitHubRepository.java b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/github/api/GitHubRepository.java
new file mode 100644
index 0000000..57eef9c
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/github/api/GitHubRepository.java
@@ -0,0 +1,24 @@
+package io.reflectoring.modules.github.api;
+
+import java.util.Objects;
+
+public class GitHubRepository {
+
+    private final  String name;
+    private final String organization;
+
+    public GitHubRepository(String name, String organization) {
+        Objects.requireNonNull(name);
+        Objects.requireNonNull(organization);
+        this.name = name;
+        this.organization = organization;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public String getOrganization() {
+        return organization;
+    }
+}
diff --git a/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/github/internal/GitHubModuleConfiguration.java b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/github/internal/GitHubModuleConfiguration.java
new file mode 100644
index 0000000..2b8662b
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/github/internal/GitHubModuleConfiguration.java
@@ -0,0 +1,14 @@
+package io.reflectoring.modules.github.internal;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+class GitHubModuleConfiguration {
+
+    @Bean
+    GitHubService gitHubService(){
+        return new GitHubService();
+    }
+
+}
diff --git a/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/github/internal/GitHubService.java b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/github/internal/GitHubService.java
new file mode 100644
index 0000000..f979146
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/github/internal/GitHubService.java
@@ -0,0 +1,35 @@
+package io.reflectoring.modules.github.internal;
+
+import io.reflectoring.modules.github.api.GitHubMutations;
+import io.reflectoring.modules.github.api.GitHubQueries;
+import io.reflectoring.modules.github.api.GitHubRepository;
+
+import java.util.Collections;
+import java.util.List;
+
+public class GitHubService implements GitHubMutations, GitHubQueries {
+
+    @Override
+    public String createRepository(String token, GitHubRepository repository) {
+        // call the GitHub API to create a repo
+        return "https://github.com/reflectoring/reflectoring.github.io";
+    }
+
+    @Override
+    public List<String> getOrganisations(String token) {
+        // call the GitHub API to get a list of organisations for the user
+        return Collections.emptyList();
+    }
+
+    @Override
+    public List<String> getRepositories(String token, String organisation) {
+        // call the GitHub API to get a list of repositories for the user
+        return Collections.emptyList();
+    }
+
+    @Override
+    public boolean repositoryExists(String token, String repositoryName, String organisation) {
+        // call the GitHub API to find out if a given repo exists
+        return false;
+    }
+}
diff --git a/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/mail/api/EmailNotificationService.java b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/mail/api/EmailNotificationService.java
new file mode 100644
index 0000000..1c9879e
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/mail/api/EmailNotificationService.java
@@ -0,0 +1,7 @@
+package io.reflectoring.modules.mail.api;
+
+public interface EmailNotificationService {
+
+    void sendEmail(String to, String subject, String text);
+
+}
diff --git a/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/mail/internal/EmailModuleConfiguration.java b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/mail/internal/EmailModuleConfiguration.java
new file mode 100644
index 0000000..8e46423
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/mail/internal/EmailModuleConfiguration.java
@@ -0,0 +1,28 @@
+package io.reflectoring.modules.mail.internal;
+
+import io.reflectoring.modules.mail.api.EmailNotificationService;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@EnableConfigurationProperties(EmailModuleConfigurationProperties.class)
+public class EmailModuleConfiguration {
+
+    private final EmailModuleConfigurationProperties configurationProperties;
+
+    public EmailModuleConfiguration(EmailModuleConfigurationProperties configurationProperties) {
+        this.configurationProperties = configurationProperties;
+    }
+
+    @Bean
+    EmailNotificationService emailNotificationService(MailClient mailClient) {
+        return new EmailNotificationServiceImpl(mailClient);
+    }
+
+    @Bean
+    MailClient mailClient() {
+        return new MailClient(configurationProperties.isEnabled());
+    }
+
+}
diff --git a/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/mail/internal/EmailModuleConfigurationProperties.java b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/mail/internal/EmailModuleConfigurationProperties.java
new file mode 100644
index 0000000..82f427e
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/mail/internal/EmailModuleConfigurationProperties.java
@@ -0,0 +1,17 @@
+package io.reflectoring.modules.mail.internal;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+
+@ConfigurationProperties(prefix = "mail")
+public class EmailModuleConfigurationProperties {
+
+    private boolean enabled;
+
+    public boolean isEnabled() {
+        return enabled;
+    }
+
+    public void setEnabled(boolean enabled) {
+        this.enabled = enabled;
+    }
+}
diff --git a/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/mail/internal/EmailNotificationServiceImpl.java b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/mail/internal/EmailNotificationServiceImpl.java
new file mode 100644
index 0000000..8caa489
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/mail/internal/EmailNotificationServiceImpl.java
@@ -0,0 +1,19 @@
+package io.reflectoring.modules.mail.internal;
+
+import io.reflectoring.modules.mail.api.EmailNotificationService;
+import org.springframework.stereotype.Component;
+
+class EmailNotificationServiceImpl implements EmailNotificationService {
+
+    private final MailClient mailClient;
+
+    public EmailNotificationServiceImpl(MailClient mailClient) {
+        this.mailClient = mailClient;
+    }
+
+    @Override
+    public void sendEmail(String to, String subject, String text) {
+        // send an email         
+    }
+
+}
diff --git a/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/mail/internal/MailClient.java b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/mail/internal/MailClient.java
new file mode 100644
index 0000000..79ba56b
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/mail/internal/MailClient.java
@@ -0,0 +1,32 @@
+package io.reflectoring.modules.mail.internal;
+
+import javax.annotation.PostConstruct;
+
+/**
+ * Internal mail server connection. This is not part of the API of the `mail` component.
+ */
+class MailClient {
+
+    private final boolean connectToMailServer;
+
+    public MailClient(boolean connectToMailServer) {
+        this.connectToMailServer = connectToMailServer;
+    }
+
+    void sendMail() {
+
+    }
+
+    /**
+     * There are many cases where a Spring application connects to external resources during startup, for example when
+     * initializing a connection pool to a database or some other service. This method just simulates a failing connection
+     * during startup. This forces us not to load this bean during integration tests.
+     */
+    @PostConstruct
+    void connectToMailServer() {
+        if(connectToMailServer) {
+            throw new RuntimeException("Could not connect to mail server!");
+        }
+    }
+
+}
diff --git a/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/rest/internal/RepositoryController.java b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/rest/internal/RepositoryController.java
new file mode 100644
index 0000000..3eebe4d
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/main/java/io/reflectoring/modules/rest/internal/RepositoryController.java
@@ -0,0 +1,46 @@
+package io.reflectoring.modules.rest.internal;
+
+import io.reflectoring.modules.github.api.GitHubMutations;
+import io.reflectoring.modules.github.api.GitHubQueries;
+import io.reflectoring.modules.github.api.GitHubRepository;
+import io.reflectoring.modules.mail.api.EmailNotificationService;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+class RepositoryController {
+
+    private final GitHubMutations gitHubMutations;
+    private final GitHubQueries gitHubQueries;
+    private final EmailNotificationService emailNotificationService;
+
+    public RepositoryController(
+            GitHubMutations gitHubMutations,
+            GitHubQueries gitHubQueries,
+            EmailNotificationService emailNotificationService
+    ) {
+        this.gitHubMutations = gitHubMutations;
+        this.gitHubQueries = gitHubQueries;
+        this.emailNotificationService = emailNotificationService;
+    }
+
+    @PostMapping("/github/repository")
+    ResponseEntity<Void> createGitHubRepository(
+            @RequestParam("token") String token,
+            @RequestParam("repositoryName") String repoName,
+            @RequestParam("organizationName") String orgName
+    ) {
+
+        if (gitHubQueries.repositoryExists(token, repoName, orgName)) {
+            return ResponseEntity.status(HttpStatus.BAD_REQUEST).build();
+        }
+        String repoUrl = gitHubMutations.createRepository(token, new GitHubRepository(repoName, orgName));
+        emailNotificationService.sendEmail("user@mail.com", "Your new repository", "Here's your new repository: " + repoUrl);
+
+        return ResponseEntity.ok().build();
+    }
+
+}
diff --git a/spring-boot/spring-boot-mocking-modules/src/main/resources/application.properties b/spring-boot/spring-boot-mocking-modules/src/main/resources/application.properties
new file mode 100644
index 0000000..8b13789
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/main/resources/application.properties
@@ -0,0 +1 @@
+
diff --git a/spring-boot/spring-boot-mocking-modules/src/test/java/io/reflectoring/modules/github/GitHubModuleMock.java b/spring-boot/spring-boot-mocking-modules/src/test/java/io/reflectoring/modules/github/GitHubModuleMock.java
new file mode 100644
index 0000000..033709a
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/test/java/io/reflectoring/modules/github/GitHubModuleMock.java
@@ -0,0 +1,51 @@
+package io.reflectoring.modules.github;
+
+import io.reflectoring.modules.github.internal.GitHubService;
+import org.mockito.Mockito;
+import org.springframework.boot.test.context.TestConfiguration;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Primary;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+
+@TestConfiguration
+public class GitHubModuleMock {
+
+    private final GitHubService gitHubServiceMock = Mockito.mock(GitHubService.class);
+
+    @Bean
+    @Primary
+    GitHubService gitHubServiceMock() {
+        return gitHubServiceMock;
+    }
+
+    public void givenCreateRepositoryReturnsUrl(String url) {
+        given(gitHubServiceMock.createRepository(any(), any())).willReturn(url);
+    }
+
+    public void givenRepositoryExists(){
+        given(gitHubServiceMock.repositoryExists(anyString(), anyString(), anyString())).willReturn(true);
+    }
+
+    public void givenRepositoryDoesNotExist(){
+        given(gitHubServiceMock.repositoryExists(anyString(), anyString(), anyString())).willReturn(false);
+    }
+
+    public void assertRepositoryCreated(){
+        verify(gitHubServiceMock).createRepository(any(), any());
+    }
+
+    public void givenDefaultState(String defaultRepositoryUrl){
+        givenRepositoryDoesNotExist();
+        givenCreateRepositoryReturnsUrl(defaultRepositoryUrl);
+    }
+
+    public void assertRepositoryNotCreated(){
+        verify(gitHubServiceMock, never()).createRepository(any(), any());
+    }
+
+}
diff --git a/spring-boot/spring-boot-mocking-modules/src/test/java/io/reflectoring/modules/mail/EmailModuleMock.java b/spring-boot/spring-boot-mocking-modules/src/test/java/io/reflectoring/modules/mail/EmailModuleMock.java
new file mode 100644
index 0000000..81d462e
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/test/java/io/reflectoring/modules/mail/EmailModuleMock.java
@@ -0,0 +1,41 @@
+package io.reflectoring.modules.mail;
+
+import io.reflectoring.modules.mail.api.EmailNotificationService;
+import org.mockito.Mockito;
+import org.springframework.boot.test.context.TestConfiguration;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Primary;
+
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.ArgumentMatchers.contains;
+import static org.mockito.Mockito.*;
+
+@TestConfiguration
+public class EmailModuleMock {
+
+    private final EmailNotificationService emailNotificationServiceMock = Mockito.mock(EmailNotificationService.class);
+
+    @Bean
+    @Primary
+    EmailNotificationService emailNotificationServiceMock() {
+        return emailNotificationServiceMock;
+    }
+
+    public void givenSendMailSucceeds() {
+        // nothing to do, the mock will simply return 0
+    }
+
+    public void givenSendMailThrowsError() {
+        doThrow(new RuntimeException("error when sending mail"))
+                .when(emailNotificationServiceMock).sendEmail(anyString(), anyString(), anyString());
+    }
+
+    public void assertSentMailContains(String repositoryUrl) {
+        verify(emailNotificationServiceMock).sendEmail(anyString(), anyString(), contains(repositoryUrl));
+    }
+
+    public void assertNoMailSent() {
+        verify(emailNotificationServiceMock, never()).sendEmail(anyString(), anyString(), anyString());
+    }
+
+}
diff --git a/spring-boot/spring-boot-mocking-modules/src/test/java/io/reflectoring/modules/rest/RepositoryControllerTest.java b/spring-boot/spring-boot-mocking-modules/src/test/java/io/reflectoring/modules/rest/RepositoryControllerTest.java
new file mode 100644
index 0000000..70a2c93
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/test/java/io/reflectoring/modules/rest/RepositoryControllerTest.java
@@ -0,0 +1,69 @@
+package io.reflectoring.modules.rest;
+
+import io.reflectoring.modules.github.GitHubModuleMock;
+import io.reflectoring.modules.mail.EmailModuleMock;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
+import org.springframework.context.annotation.Import;
+import org.springframework.test.context.TestPropertySource;
+import org.springframework.test.web.servlet.MockMvc;
+
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+@WebMvcTest
+@TestPropertySource(properties = "mail.enabled=false")
+@Import({
+        GitHubModuleMock.class,
+        EmailModuleMock.class
+})
+class RepositoryControllerTest {
+
+    @Autowired
+    private MockMvc mockMvc;
+
+    @Autowired
+    private EmailModuleMock emailModuleMock;
+
+    @Autowired
+    private GitHubModuleMock gitHubModuleMock;
+
+    @Test
+    void givenRepositoryDoesNotExist_thenRepositoryIsCreatedSuccessfully() throws Exception {
+
+        String repositoryUrl = "https://github.com/reflectoring/reflectoring.github.io";
+
+        gitHubModuleMock.givenDefaultState(repositoryUrl);
+        emailModuleMock.givenSendMailSucceeds();
+
+        mockMvc.perform(post("/github/repository")
+                .param("token", "123")
+                .param("repositoryName", "foo")
+                .param("organizationName", "bar"))
+                .andExpect(status().is(200));
+
+        emailModuleMock.assertSentMailContains(repositoryUrl);
+        gitHubModuleMock.assertRepositoryCreated();
+    }
+
+    @Test
+    void givenRepositoryExists_thenReturnsBadRequest() throws Exception {
+
+        String repositoryUrl = "https://github.com/reflectoring/reflectoring.github.io";
+
+        gitHubModuleMock.givenDefaultState(repositoryUrl);
+        gitHubModuleMock.givenRepositoryExists();
+        emailModuleMock.givenSendMailSucceeds();
+
+        mockMvc.perform(post("/github/repository")
+                .param("token", "123")
+                .param("repositoryName", "foo")
+                .param("organizationName", "bar"))
+                .andExpect(status().is(400));
+
+        emailModuleMock.assertNoMailSent();
+        gitHubModuleMock.assertRepositoryNotCreated();
+    }
+
+}
\ No newline at end of file
diff --git a/spring-boot/spring-boot-mocking-modules/src/test/java/io/reflectoring/modules/rest/RepositoryControllerTestWithoutModuleMocks.java b/spring-boot/spring-boot-mocking-modules/src/test/java/io/reflectoring/modules/rest/RepositoryControllerTestWithoutModuleMocks.java
new file mode 100644
index 0000000..2e249ed
--- /dev/null
+++ b/spring-boot/spring-boot-mocking-modules/src/test/java/io/reflectoring/modules/rest/RepositoryControllerTestWithoutModuleMocks.java
@@ -0,0 +1,69 @@
+package io.reflectoring.modules.rest;
+
+import io.reflectoring.modules.github.api.GitHubMutations;
+import io.reflectoring.modules.github.api.GitHubQueries;
+import io.reflectoring.modules.mail.api.EmailNotificationService;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
+import org.springframework.boot.test.mock.mockito.MockBean;
+import org.springframework.test.context.TestPropertySource;
+import org.springframework.test.web.servlet.MockMvc;
+
+import static org.mockito.ArgumentMatchers.*;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.verify;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+@WebMvcTest
+@TestPropertySource(properties = "mail.enabled=false")
+class RepositoryControllerTestWithoutModuleMocks {
+
+    @Autowired
+    private MockMvc mockMvc;
+
+    @MockBean
+    private GitHubMutations gitHubMutations;
+
+    @MockBean
+    private GitHubQueries gitHubQueries;
+
+    @MockBean
+    private EmailNotificationService emailNotificationService;
+
+    @Test
+    void givenRepositoryDoesNotExist_thenRepositoryIsCreatedSuccessfully() throws Exception {
+
+        String repositoryUrl = "https://github.com/reflectoring/reflectoring.github.io";
+
+        given(gitHubQueries.repositoryExists(
+                anyString(),
+                anyString(),
+                anyString())
+        ).willReturn(false);
+
+        given(gitHubMutations.createRepository(
+                any(),
+                any())
+        ).willReturn(repositoryUrl);
+
+        mockMvc.perform(post("/github/repository")
+                .param("token", "123")
+                .param("repositoryName", "foo")
+                .param("organizationName", "bar"))
+                .andExpect(status().is(200));
+
+        verify(emailNotificationService).sendEmail(
+                anyString(),
+                anyString(),
+                contains(repositoryUrl)
+        );
+
+        verify(gitHubMutations).createRepository(
+                any(),
+                any()
+        );
+    }
+
+}
\ No newline at end of file