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How to configure Surefire to include '*Spec' Spock tests?

How can I make sure that certain tests are executed in a Maven build and not silently ignored?
I was recently forced to switch to Groovy 3. As a result, I updated my Spock version as well. Unfortunately, I missed the fact that Spock 2 requires JUnit 5. I only had JUnit 4 and Spock tests, therefore the Maven Surefire plugin used the JUnit 4 provider to execute tests. All Spock test were ignored. I just noticed this by accident.
I'm looking for a way to check if certain (or any) tests ending in *Spec are among the tests executed. I looked at the Maven Surefire and the Maven Enforcer plugin but could not find anything which suits my needs. If I'm skipping test execution completely this check should not fail.
Edit: This is a shortened version of the Spock example project as kriegaex suggested posting some pom.xml files. The problem applies to all Java projects, though. To me, a solution within the build process of the project itself would be superior to configuring CI/CD jobs as this can can easily be forgotten when moving/migrating the project to another CI pipeline.
<?xml version="1.0"?>
<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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.spockframework</groupId>
<artifactId>spock-example</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>jar</packaging>
<name>Spock Framework - Example Project</name>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<groovy.version>3.0.7</groovy.version>
</properties>
<build>
<plugins>
<!-- Mandatory plugins for using Spock -->
<plugin>
<!-- The gmavenplus plugin is used to compile Groovy code. To learn more about this plugin,
visit https://github.com/groovy/GMavenPlus/wiki -->
<groupId>org.codehaus.gmavenplus</groupId>
<artifactId>gmavenplus-plugin</artifactId>
<version>1.12.0</version>
<executions>
<execution>
<goals>
<goal>compile</goal>
<goal>compileTests</goal>
</goals>
</execution>
</executions>
</plugin>
<!-- Optional plugins for using Spock -->
<!-- Only required if names of spec classes don't match default Surefire patterns (`*Test` etc.) -->
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>3.0.0-M5</version>
<configuration>
<useModulePath>false</useModulePath> <!-- https://issues.apache.org/jira/browse/SUREFIRE-1809 -->
<useFile>false</useFile>
<includes>
<include>**/*Test</include>
<include>**/*Spec</include>
</includes>
</configuration>
</plugin>
</plugins>
</build>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.spockframework</groupId>
<artifactId>spock-bom</artifactId>
<version>2.0-M5-groovy-3.0</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<!-- Mandatory dependencies for using Spock -->
<dependency>
<groupId>org.spockframework</groupId>
<artifactId>spock-core</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.spockframework</groupId>
<artifactId>spock-junit4</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
</project>

Sorry for the misunderstanding about spock-junit4. You only need that if you want to run JUnit 4 extensions, such as PowerMock runner, under Spock 2. If you want to run JUnit 4 tests beside Spock 2 tests, you need org.junit.vintage:junit-vintage-engine:5.7.1 for Spock 2.0-M5. Adding that dependency, fixes your POM for me.
However, I took the liberty to upgrade to Spock 2.0 final, Groovy 3.0.8 and JUnit 5.7.2, all in harmony with Spock 2.0. If you use a default Maven directory layout and name your Spock specs src/test/groovy/*Test instead of *Spec, you can even do without the Surefire class name filter. You should however specify Java source and target levels. Without them, my JDK complained about the default 1.5.
<?xml version="1.0"?>
<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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.spockframework</groupId>
<artifactId>spock-example</artifactId>
<version>1.0-SNAPSHOT</version>
<name>Spock Framework - Example Project</name>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
<groovy.version>3.0.8</groovy.version>
</properties>
<build>
<plugins>
<!-- Mandatory plugins for using Spock -->
<plugin>
<groupId>org.codehaus.gmavenplus</groupId>
<artifactId>gmavenplus-plugin</artifactId>
<version>1.12.0</version>
<executions>
<execution>
<goals>
<goal>compile</goal>
<goal>compileTests</goal>
</goals>
</execution>
</executions>
</plugin>
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>3.0.0-M5</version>
<configuration>
<useModulePath>false</useModulePath> <!-- https://issues.apache.org/jira/browse/SUREFIRE-1809 -->
</configuration>
</plugin>
</plugins>
</build>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.spockframework</groupId>
<artifactId>spock-bom</artifactId>
<version>2.0-groovy-3.0</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>org.junit</groupId>
<artifactId>junit-bom</artifactId>
<version>5.7.2</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.spockframework</groupId>
<artifactId>spock-core</artifactId>
<scope>test</scope>
</dependency>
<!-- Required if you want to run JUnit 4 tests alongside Spock 2 -->
<dependency>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
</project>
P.S.: Actually, first I wanted to close your question as a duplicate of that one. But because since then the version numbers have changed a bit, I thought I would post a new answer here for your convenience.
Update: You can make sure that both testes named *Test and *Spec are executed, by fixing the filter in your question by adding .java or .class extensions. Weirdly enough, .groovy will not work, which is a known Surefire quirk.
<includes>
<include>**/*Test.class</include>
<include>**/*Spec.class</include>
</includes>
or
<includes>
<include>**/*Test.java</include>
<include>**/*Spec.java</include>
</includes>

Exclude test for some projects

Sorry Im newbie in Java and I wonder how to avoid test execution of my dependencies projects.
I have a Proj3 which has two dependencies, Proj1 and Proj2 (among other things).
If I execute mvn clean install not only execute tests of my current Proj3 but also from my dependencies Proj1 and Proj2.
<?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>com.proj.environment.tests.api</groupId>
<artifactId>environment_Api_Tests</artifactId>
<version>437r21</version>
<packaging>pom</packaging>
<properties>
<cucumber.version>4.3.1</cucumber.version>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.version>437r21</project.version>
</properties>
<dependencies>
<dependency>
<groupId>io.cucumber</groupId>
<artifactId>cucumber-java</artifactId>
<version>${cucumber.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>io.cucumber</groupId>
<artifactId>cucumber-junit</artifactId>
<version>${cucumber.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.proj.environment</groupId>
<artifactId>Proj1</artifactId>
<version>${project.version}</version>
</dependency>
<dependency>
<groupId>com.proj.environment</groupId>
<artifactId>Proj2</artifactId>
<version>${project.version}</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.7.0</version>
<configuration>
<encoding>UTF-8</encoding>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.18.1</version>
<configuration>
<testFailureIgnore>true</testFailureIgnore>
<includes>
<exclude>**/*Test.java</exclude>
</includes>
</configuration>
</plugin>
</plugins>
</build>
<modules>
<module>../Proj1</module>
<module>../Proj2</module>
</modules>
Many thanks,

The POM you are showing is for environment_Api_Tests project which is aggregation (parent) project. That means
... if a Maven command is invoked against the parent project, that Maven command will then be executed to the parent's modules as well.
Thus it is not very clear what exactly is your case.
Depending on what it has to do with the Proj3 you mentioned, there are different answers:
If the environment_Api_Tests project (the POM you posted) is what you call Proj3
It is perfectly normal to execute commands against its modules (do not confuse it with dependencies) and it really makes no sense to exclude tests from modules. Moreover you can not have tests in aggregation (parent) project itself. So if you only want to execute some modules, then it's best to introduce another aggregation project with only those modules. You can further aggregate aggregation projects.
The <dependencies> here have nothing to do with that. The only thing that section does in a aggregation project is to provide dependencies for all <modules>. In your case that means that:
Proj1 depends on Proj1 and Proj2.
Proj2 depends on Proj1 and Proj2.
which is probably not what you want!
If there is another Proj3 that is also a module in environment_Api_Tests
Then you just need to execute the tests on that project and not on environment_Api_Tests. Even if Proj3 depends on Proj1 and Proj2 their tests will not be executed
If Proj3 is environment_Api_Tests but it was not meant to be an aggregation project
Then you need to change the packaging from pom to jar (or whatever your target is) and remove the <modules> but keep the <dependencies>. That way the project can have own tests and will not execute tests of dependencies.
Note on test dependencies
One thing to keep in mind is how test dependencies work in multi-module projects. If tests in one module depends on tests in another module, you will have to create a jar containing test classes.

Maven Read properties plugin doesn't substitute values for dependencies

Following is my project structure.
test-proj
|_ src
|_main
| |_java
|_test
|_java
|_prop.properties
|_pom.xml
And my pom.xml
<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>com.sample</groupId>
<artifactId>test</artifactId>
<version>1.0-SNAPSHOT</version>
<build>
<!-- The resources tag will be used if prop file is under src location. -->
<!-- <resources>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
</resource>
</resources> -->
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>properties-maven-plugin</artifactId>
<version>1.0.0</version>
<executions>
<execution>
<phase>initialize</phase>
<goals>
<goal>read-project-properties</goal>
</goals>
<configuration>
<files>
<file>${basedir}/prop.properties</file>
</files>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>${spring-version}</version>
</dependency>
</dependencies>
</project>
Prop.properties file has
spring-version=3.1.0.RELEASE
I have tried to use maven-read properties plugin to read the properties and substitute the same in the place of spring version. But it throws up error saying 'dependencies.dependency.version' for org.springframework:spring-beans:jar must be a valid version but is '${spring-version}'.
I tried to use validate phase instead of initialize in the maven execution phase. But still the problem persists. Instead of context path, i tried replacing the property file location to be an absolute path D:\test-proj\prop.properties in configuration which didnt help me either. I am using maven compiler plugin version 2.3.2. Am I missing something? Please let me know if its feasible to substitute dependency versions by some other plugin as well.
Note: I will not be able to use parent-child pom relationship as all my projects are modular and they don't depend on the same parent

If you want multiple unrelated project share dependecies version you can use Bill of Material concept http://howtodoinjava.com/maven/maven-bom-bill-of-materials-dependency/
Create unrelated BOM project with packaging pom. Add shared dependencies to the project
Each your project must import the BOM project
Below is snippet from the example page
How to add BOM [Bill Of Materials] dependency
Maven provides a tag dependencyManagement for this purpose. You need to add the bom information in this tag as follows. I am taking the example of Spring bom file.
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-framework-bom</artifactId>
<version>4.0.1.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
An added benefit of using the BOM is that you no longer need to specify the version attribute when depending on Spring Framework artifacts. So it will work perfectly fine.
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
</dependency>

I cannot imagine that this is going to work. AFAIU Maven has to resolve dependencies prior to any build execution since how should it be able to create a proper classpath for executions otherwise?
Re:
I will not be able to use parent-child pom relationship as all my projects are modular and they don't depend on the same parent.
I think you are able. Establish a super-parent POM that contains appropriate setting(s) to be inherited by all and make all your projects' parents childs of this:
+- super-parent
+- pom.xml ... containing setting(s) for all
+- parent-project-1
+- ...
+- parent-project-2
+- ...
+- ...

Classloader with Maven built jar

I am working on a project which contains a number of subprojects. The structure is something like Project 1, Project 2 and ProjectClassLoader.
Using separate configuration files, I pass in the binary names of the classes from Projects 1 and 2 that need to be loaded each time as arguments to the ProjectClassLoader project.
The ProjectClassLoader gets a handle to the system classloader
ClassLoader loader = ClassLoader.getSystemClassLoader();
which in theory allows it to load any classes which are contained in the classpath.
I'm using Maven to build the projects and handle their associated dependences. Thus each project has it's own individual pom.xml file. The ProjectClassLoader defines a parent pom.xml over Projects 1 and 2 which inherit from this. The parent pom contains dependency entries for both Project 1 and 2.
My understanding was that any dependencies specified in the pom.xml files of these projects would get added to the classpath at runtime. However when trying to load classes using the system classloader, I'm getting class not found execptions.
I have tried using the mvn:exec plugin which I understand includes the dependencies in the classpath when executing jars on the command line but this has not worked.
I'd grately appreciate any help in furthering my understanding of why I can load the classes even though the dependencies are defined in the pom...Thanks in advance

Can you check if your pom matches this configuration a bit?
<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">
...
<properties>
...
<exec.maven.plugin.version>1.2.1</exec.maven.plugin.version>
...
</properties>
<build>
<plugins>
...
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
</plugin>
...
</plugins>
<pluginManagement>
<plugins>
...
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>${exec.maven.plugin.version}</version>
<configuration>
<executable>java</executable>
<arguments>
<argument>-classpath</argument>
<!-- automatically creates the classpath using all project dependencies, also adding the project build directory -->
<classpath />
<argument>com.example.Main</argument><!-- your mainClass -->
</arguments>
</configuration>
</plugin>
...
</plugins>
</pluginManagement>
</build>
<dependencies>
...
<dependency>
<groupId>groupId.for.project1</groupId>
<artifactId>project1</artifactId>
</dependency>
<dependency>
<groupId>groupId.for.project2</groupId>
<artifactId>project2</artifactId>
</dependency>
...
</dependencies>
<dependencyManagement>
<dependencies>
...
<dependency>
<groupId>groupId.for.project1</groupId>
<artifactId>project1</artifactId>
<version>${project1.version}</version>
</dependency>
<dependency>
<groupId>groupId.for.project2</groupId>
<artifactId>project2</artifactId>
<version>${project2.version}</version>
</dependency>
...
</dependencies>
</dependencyManagement>
...
</project>
Where you fill them with the correct artifacts.
You should then be able to start it with:
mvn exec:exec
Can you post your configuration for your pom plz if it doesn't match, that way it's easier to understand what exactly you currently have in your pom.

Maven: javax.servlet specification deployed

I've a web application configured with Maven which uses a library, also configured with Maven and when I package geronimo-servlet_3.0_spec-1.0.jar is included in WEB-INF/lib and I don't understand why.
I check the library with mvn dependency:tree
$ mvn dependency:tree | grep geronimo
[INFO] +- org.apache.geronimo.specs:geronimo-servlet_3.0_spec:jar:1.0:provided
I check my web app:
$ mvn dependency:tree | grep geronimo
$
However when I run mvn:package the file gets included in WEB-INF/lib.
When I run mvn tomcat:run I can see:
INFO: validateJarFile(/home/stivlo/workspace/private/src/main/webapp/WEB-INF/lib/geronimo-servlet_3.0_spec-1.0.jar) - jar not loaded. See Servlet Spec 2.3, section 9.7.2. Offending class: javax/servlet/Servlet.class
Why and how to avoid? Thank you.
UPDATE 1: as requested I add the pom.xml
<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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.obliquid</groupId>
<artifactId>test-webapp</artifactId>
<packaging>war</packaging>
<version>1.0-SNAPSHOT</version>
<name>private webapp</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<repositories>
<!-- For Jakarta ORO -->
<repository>
<id>mvnsearch</id>
<name>Maven Search</name>
<url>http://www.mvnsearch.org/maven2/</url>
</repository>
</repositories>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.8.2</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.obliquid.helpers</groupId>
<artifactId>obliquid-helpers</artifactId>
<version>0.9-SNAPSHOT</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>2.4</version>
<scope>provided</scope>
</dependency>
</dependencies>
<build>
<finalName>private</finalName>
</build>
</project>
UPDATE 2: I followed the advice of Stephen C and modified the build section as follows:
<build>
<finalName>private</finalName>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war</artifactId>
<version>2.1</version>
<configuration>
<overlays>
<overlay>
<groupId>org.obliquid</groupId>
<artifactId>test-webapp</artifactId>
<excludes>
<exclude>WEB-INF/lib/geronimo-servlet_3.0_spec-1.0.jar</exclude>
</excludes>
</overlay>
</overlays>
</configuration>
</plugin>
</plugins>
</build>
However geronimo*.jar still gets included. I guess I've made a mistake in this configuration.
UPDATE 3: Stephen C. says that I should use
the groupId the artifactId of the WAR
file that contains the JAR file(s)
that you are trying to exclude.
I didn't know that WAR files could have a groupId and artifactId, in fact in my pom.xml I don't see any. My project builds a WAR file and has a groupId and an artifactId and those were the ones I tested above without success.
The dependency causing the problem is the following (is a JAR, not a WAR):
<dependency>
<groupId>org.obliquid.helpers</groupId>
<artifactId>obliquid-helpers</artifactId>
<version>0.9-SNAPSHOT</version>
<scope>compile</scope>
</dependency>
If I try to use the groupId and artifactId listed in this dependency I've the following error:
[ERROR] Failed to execute goal
org.apache.maven.plugins:maven-war-plugin:2.1.1:war
(default-war) on project test-webapp:
overlay [ id
org.obliquid.helpers:obliquid-helpers]
is not a dependency of the project. ->
[Help 1]
If I try to use the groupId and artifactId of the JAR included by org.obliquid.helpers:
<groupId>org.apache.geronimo.specs</groupId>
<artifactId>geronimo-servlet_3.0_spec</artifactId>)
I have the same error.
[ERROR] Failed to execute goal
org.apache.maven.plugins:maven-war-plugin:2.1.1:war
(default-war) on project test-webapp:
overlay [ id
org.apache.geronimo.specs:geronimo-servlet_3.0_spec]
is not a dependency of the project. ->
[Help 1]
Reading the War plugin documentation, I found a section about creating skinny WARs. So I tried the following:
<build>
<finalName>private</finalName>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>2.1.1</version>
<configuration>
<packagingExcludes>WEB-INF/lib/geronimo-servlet_3.0_spec-1.0.jar</packagingExcludes>
</configuration>
</plugin>
</plugins>
</build>
Still without any success, geronimo-servlet_3.0_spec-1.0.jar is still there!
<groupId>org.obliquid.helpers</groupId>
<artifactId>obliquid-helpers</artifactId>
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-war-plugin:2.1.1:war (default-war) on project test-webapp: overlay [ id org.obliquid.helpers:obliquid-helpers] is not a dependency of the project. -> [Help 1]
<groupId>org.apache.geronimo.specs</groupId>
<artifactId>geronimo-servlet_3.0_spec</artifactId>
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-war-plugin:2.1.1:war (default-war) on project test-webapp: overlay [ id org.apache.geronimo.specs:geronimo-servlet_3.0_spec] is not a dependency of the project. -> [Help 1]
UPDATE 4: I discovered that the target/private.war file is not a zip of target/private/ directory, but the exclusions are done at packaging time and not by deleting files in target/private/ -- This means, I've to re-test all the things I did before.
Suggestion of gouki: doesn't work, the JAR is still there also in the WAR file.
Suggestion of Stephen C., maybe mis-understood: actually I just noticed that the pom.xml is always invalid whatever groupId/artifactId I put of the three possibilities explained above. So they didn't work for me.
What I found in the documentation (packagingExcludes), works.
Now, if I had to choose one of he answers I would choose Stephen C., because he helped me pointing at the documentation of the WAR plugin (I was reading in the wrong places). However I'd accept an answer that doesn't work, at least in the way I tried (probably wrong). So I'm not going to accept any answer, and add a new answer myself with the final working configuration.
UPDATE 5: I post the relevant part of the pom.xml of obliquid-helpers, that mentions geronimo-servlet_3.0_spec. I've marked it optional and with scope provided, still it gets included by a web-app, unless I mark it as "packagingExclude" in the maven-war-plugin configuration.
<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>org.obliquid.helpers</groupId>
<artifactId>obliquid-helpers</artifactId>
<version>0.9-SNAPSHOT</version>
<packaging>jar</packaging>
<name>obliquid-helpers</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<repositories>
[...]
</repositories>
<dependencies>
[...]
<dependency>
<groupId>org.apache.geronimo.specs</groupId>
<artifactId>geronimo-servlet_3.0_spec</artifactId>
<version>1.0</version>
<scope>provided</scope>
<optional>true</optional>
</dependency>
</dependencies>
</project>

Clearly, something has a dependency on that JAR file. If it is not showing up in the dependency tree, perhaps it is due to a dependency of your webapp WAR file on another WAR file that has this dependency.
If that is the case, then you could get add an <excludes> to the <overlay> element of the build descriptor for the WAR file plugin; e.g.
...
<build>
<finalName>webapp</finalName>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>2.1</version>
<configuration>
<overlays>
<overlay>
<groupId>xxx</groupId>
<artifactId>yyy</artifactId>
<excludes>
<exclude>WEB-INF/lib/whatever.jar</exclude>
</excludes>
</overlay>
</overlays>
</configuration>
</plugin>
</plugins>
</build>
...
If you are using WAR file overlays, you should always include the clean target in the build. Otherwise you can get old dependencies hanging around in the WAR file. (IIRC, there is a Warning in the Maven output each time you build an overlaid WAR without cleaning!)
In fact, this could be the root cause of your problems. For instance, if previously you had the "geronimo" as an ordinary dependency and you haven't run mvn clean since then, the JAR file could still be hanging around.

Based from your pom.xml, the only dependency that might have dependency on geronimo servlet is
<dependency>
<groupId>org.obliquid.helpers</groupId>
<artifactId>obliquid-helpers</artifactId>
<version>0.9-SNAPSHOT</version>
<scope>compile</scope>
</dependency>
Can you try excluding the geronimo in this dependency?
<dependency>
<groupId>org.obliquid.helpers</groupId>
<artifactId>obliquid-helpers</artifactId>
<version>0.9-SNAPSHOT</version>
<scope>compile</scope>
<exclusions>
<exclusion>
<groupId>org.apache.geronimo.specs</groupId>
<artifactId>geronimo-servlet_3.0_spec</artifactId>
</exclusion>
</exclusions>
</dependency>

First I want to thank gouki and Stephen C. for helping me. However their proposed solution didn't work for me. I'm grateful to them, but I can't accept their answer, because it would be misleading since it didn't work for this problem. I've upvoted Stephen C. answer, because he pointed me to the right documentation, which was essential to solve the problem.
Reading the WAR plugin documentation, especially the war:war mojo section, I've found an example on how to create Skinny WARs, which did the trick. So here is below the working configuration, to be added to the build section:
<build>
<finalName>private</finalName>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>2.1.1</version>
<configuration>
<packagingExcludes>WEB-INF/lib/geronimo-servlet_3.0_spec-1.0.jar</packagingExcludes>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<classpathPrefix>lib/</classpathPrefix>
</manifest>
</archive>
</configuration>
</plugin>
</plugins>
</build>
The archive part is probably not really needed, but I will find out when I deploy the WAR. The part that does the trick is the packagingExcludes tag, that can contain a comma separated list of tokens to exclude from the WAR before packaging.