diff --git a/api/src/main/groovy/com/jessebrault/ssg/buildscript/dsl/AbstractBuildDelegate.groovy b/api/src/main/groovy/com/jessebrault/ssg/buildscript/dsl/AbstractBuildDelegate.groovy
index 636e974..6bcdfda 100644
--- a/api/src/main/groovy/com/jessebrault/ssg/buildscript/dsl/AbstractBuildDelegate.groovy
+++ b/api/src/main/groovy/com/jessebrault/ssg/buildscript/dsl/AbstractBuildDelegate.groovy
@@ -22,7 +22,8 @@ abstract class AbstractBuildDelegate<T> {
         this.siteSpecClosures.inject(SiteSpec.getBlank()) { acc, closure ->
             def d = new SiteSpecDelegate()
             closure.delegate = d
-            closure.resolveStrategy = DELEGATE_FIRST
+            //noinspection UnnecessaryQualifiedReference
+            closure.resolveStrategy = Closure.DELEGATE_FIRST
             closure()
             acc + d.getResult()
         }
@@ -32,7 +33,8 @@ abstract class AbstractBuildDelegate<T> {
         this.globalsClosures.inject([:] as Map<String, Object>) { acc, closure ->
             def d = new GlobalsDelegate()
             closure.delegate = d
-            closure.resolveStrategy = DELEGATE_FIRST
+            //noinspection UnnecessaryQualifiedReference
+            closure.resolveStrategy = Closure.DELEGATE_FIRST
             closure()
             acc + d.getResult()
         }
@@ -42,7 +44,8 @@ abstract class AbstractBuildDelegate<T> {
         this.typesClosures.inject(TypesContainer.getEmpty()) { acc, closure ->
             def d = new TypesDelegate()
             closure.delegate = d
-            closure.resolveStrategy = DELEGATE_FIRST
+            //noinspection UnnecessaryQualifiedReference
+            closure.resolveStrategy = Closure.DELEGATE_FIRST
             closure()
             acc + d.getResult()
         }
@@ -52,7 +55,8 @@ abstract class AbstractBuildDelegate<T> {
         this.sourcesClosures.inject(SourceProviders.getEmpty()) { acc, closure ->
             def d = new SourceProvidersDelegate()
             closure.delegate = d
-            closure.resolveStrategy = DELEGATE_FIRST
+            //noinspection UnnecessaryQualifiedReference
+            closure.resolveStrategy = Closure.DELEGATE_FIRST
             closure(typesContainer)
             acc + d.getResult()
         }
@@ -62,7 +66,8 @@ abstract class AbstractBuildDelegate<T> {
        this.taskFactoriesClosures.inject([:] as Map<String, TaskFactorySpec>) { acc, closure ->
             def d = new TaskFactoriesDelegate()
             closure.delegate = d
-            closure.resolveStrategy = DELEGATE_FIRST
+           //noinspection UnnecessaryQualifiedReference
+           closure.resolveStrategy = Closure.DELEGATE_FIRST
             closure(sourceProviders)
             def specs = d.getResult()
             specs.forEach { name, spec ->
diff --git a/api/src/main/groovy/com/jessebrault/ssg/buildscript/dsl/TaskFactoriesDelegate.groovy b/api/src/main/groovy/com/jessebrault/ssg/buildscript/dsl/TaskFactoriesDelegate.groovy
index 3c82fcc..41e25f7 100644
--- a/api/src/main/groovy/com/jessebrault/ssg/buildscript/dsl/TaskFactoriesDelegate.groovy
+++ b/api/src/main/groovy/com/jessebrault/ssg/buildscript/dsl/TaskFactoriesDelegate.groovy
@@ -30,7 +30,11 @@ final class TaskFactoriesDelegate {
         this.specs[name] = new TaskFactorySpec<>(factorySupplier, [factoryConfigurator])
     }
 
-    def <T extends TaskFactory> void configure(String name, Class<T> factoryClass, Consumer<T> factoryConfigureClosure) {
+    def <T extends TaskFactory> void configure(
+            String name,
+            Class<T> factoryClass, // Dummy so we get better auto-complete
+            Consumer<T> factoryConfigureClosure
+    ) {
         if (!this.specs.containsKey(name)) {
             throw new IllegalArgumentException("there is no TaskFactory registered by name ${ name }")
         }
diff --git a/api/src/main/groovy/com/jessebrault/ssg/provider/AbstractCollectionProvider.groovy b/api/src/main/groovy/com/jessebrault/ssg/provider/AbstractCollectionProvider.groovy
index 215e08e..d08d5ca 100644
--- a/api/src/main/groovy/com/jessebrault/ssg/provider/AbstractCollectionProvider.groovy
+++ b/api/src/main/groovy/com/jessebrault/ssg/provider/AbstractCollectionProvider.groovy
@@ -1,19 +1,48 @@
 package com.jessebrault.ssg.provider
 
+import groovy.transform.EqualsAndHashCode
+import groovy.transform.NullCheck
+import groovy.transform.TupleConstructor
+
+@TupleConstructor(defaults = false, includeFields = true)
+@NullCheck(includeGenerated = true)
+@EqualsAndHashCode(includeFields = true)
 abstract class AbstractCollectionProvider<T> implements CollectionProvider<T> {
 
+    static <T> CollectionProvider<T> concat(
+            CollectionProvider<T> cp,
+            Provider<T> p
+    ) {
+        new SupplierBasedCollectionProvider<>([cp], [p], {
+            [*cp.provide(), p.provide()]
+        })
+    }
+
     static <T> CollectionProvider<T> concat(
             CollectionProvider<T> cp0,
             CollectionProvider<T> cp1
     ) {
-        SupplierBasedCollectionProvider.get {
+        new SupplierBasedCollectionProvider<>([cp0, cp1], [], {
             cp0.provide() + cp1.provide()
-        }
+        })
+    }
+
+    private final Collection<CollectionProvider<T>> collectionProviderChildren
+    private final Collection<Provider<T>> providerChildren
+
+    @Override
+    boolean contains(Provider<T> provider) {
+        provider in this
+    }
+
+    @Override
+    boolean contains(CollectionProvider<T> collectionProvider) {
+        collectionProvider in this
     }
 
     @Override
     CollectionProvider<T> plus(Provider<T> other) {
-        concat(this, other as CollectionProvider<T>)
+        concat(this, other)
     }
 
     @Override
@@ -21,4 +50,23 @@ abstract class AbstractCollectionProvider<T> implements CollectionProvider<T> {
         concat(this, other)
     }
 
+    @Override
+    boolean isCase(Provider<T> provider) {
+        provider in this.providerChildren || this.providerChildren.inject(false) { acc, childProvider ->
+            acc || provider in childProvider
+        }
+    }
+
+    @Override
+    boolean isCase(CollectionProvider<T> collectionProvider) {
+        collectionProvider == this
+                || collectionProvider in this.collectionProviderChildren
+                || this.collectionProviderChildren.inject(
+                        false,
+                        { acc, childCollectionProvider ->
+                            acc || collectionProvider in childCollectionProvider
+                        }
+                )
+    }
+
 }
diff --git a/api/src/main/groovy/com/jessebrault/ssg/provider/AbstractProvider.groovy b/api/src/main/groovy/com/jessebrault/ssg/provider/AbstractProvider.groovy
index 2cf51e1..9d3272a 100644
--- a/api/src/main/groovy/com/jessebrault/ssg/provider/AbstractProvider.groovy
+++ b/api/src/main/groovy/com/jessebrault/ssg/provider/AbstractProvider.groovy
@@ -6,9 +6,9 @@ abstract class AbstractProvider<T> implements Provider<T> {
             Provider<T> p0,
             Provider<T> p1
     ) {
-        SupplierBasedCollectionProvider.get {
+        new SupplierBasedCollectionProvider<>({
             [p0.provide(), p1.provide()]
-        }
+        })
     }
 
     @Override
@@ -18,9 +18,9 @@ abstract class AbstractProvider<T> implements Provider<T> {
 
     @Override
     CollectionProvider<T> asType(Class<CollectionProvider> collectionProviderClass) {
-        SupplierBasedCollectionProvider.get {
+        new SupplierBasedCollectionProvider<>({
             [this.provide() as T]
-        }
+        })
     }
 
 }
diff --git a/api/src/main/groovy/com/jessebrault/ssg/provider/CollectionProvider.groovy b/api/src/main/groovy/com/jessebrault/ssg/provider/CollectionProvider.groovy
index a338817..03a6aa9 100644
--- a/api/src/main/groovy/com/jessebrault/ssg/provider/CollectionProvider.groovy
+++ b/api/src/main/groovy/com/jessebrault/ssg/provider/CollectionProvider.groovy
@@ -2,6 +2,13 @@ package com.jessebrault.ssg.provider
 
 interface CollectionProvider<T> {
     Collection<T> provide()
+
+    boolean contains(Provider<T> provider)
+    boolean contains(CollectionProvider<T> collectionProvider)
+
     CollectionProvider<T> plus(Provider<T> other)
     CollectionProvider<T> plus(CollectionProvider<T> other)
+
+    boolean isCase(Provider<T> provider)
+    boolean isCase(CollectionProvider<T> collectionProvider)
 }
\ No newline at end of file
diff --git a/api/src/main/groovy/com/jessebrault/ssg/provider/FileBasedCollectionProvider.groovy b/api/src/main/groovy/com/jessebrault/ssg/provider/FileBasedCollectionProvider.groovy
index b5aa37a..b9a4afa 100644
--- a/api/src/main/groovy/com/jessebrault/ssg/provider/FileBasedCollectionProvider.groovy
+++ b/api/src/main/groovy/com/jessebrault/ssg/provider/FileBasedCollectionProvider.groovy
@@ -5,7 +5,6 @@ import groovy.io.FileType
 import groovy.transform.EqualsAndHashCode
 import groovy.transform.NullCheck
 import groovy.transform.PackageScope
-import groovy.transform.TupleConstructor
 import org.jetbrains.annotations.Nullable
 import org.slf4j.Logger
 import org.slf4j.LoggerFactory
@@ -13,9 +12,8 @@ import org.slf4j.LoggerFactory
 import java.util.function.BiFunction
 
 @PackageScope
-@TupleConstructor(includeFields = true, defaults = false)
-@NullCheck(includeGenerated = true)
-@EqualsAndHashCode(includeFields = true)
+@NullCheck
+@EqualsAndHashCode(includeFields = true, callSuper = true)
 final class FileBasedCollectionProvider<T> extends AbstractCollectionProvider<T> {
 
     private static final Logger logger = LoggerFactory.getLogger(FileBasedCollectionProvider)
@@ -23,6 +21,12 @@ final class FileBasedCollectionProvider<T> extends AbstractCollectionProvider<T>
     private final File baseDirectory
     private final BiFunction<File, String, @Nullable T> elementFunction
 
+    FileBasedCollectionProvider(File baseDirectory, BiFunction<File, String, T> elementFunction) {
+        super([], [])
+        this.baseDirectory = baseDirectory
+        this.elementFunction = elementFunction
+    }
+
     @Override
     Collection<T> provide() {
         if (!this.baseDirectory.isDirectory()) {
diff --git a/api/src/main/groovy/com/jessebrault/ssg/provider/SimpleCollectionProvider.groovy b/api/src/main/groovy/com/jessebrault/ssg/provider/SimpleCollectionProvider.groovy
index 2721ad8..374807d 100644
--- a/api/src/main/groovy/com/jessebrault/ssg/provider/SimpleCollectionProvider.groovy
+++ b/api/src/main/groovy/com/jessebrault/ssg/provider/SimpleCollectionProvider.groovy
@@ -3,16 +3,19 @@ package com.jessebrault.ssg.provider
 import groovy.transform.EqualsAndHashCode
 import groovy.transform.NullCheck
 import groovy.transform.PackageScope
-import groovy.transform.TupleConstructor
 
 @PackageScope
-@TupleConstructor(defaults = false, includeFields = true)
-@NullCheck(includeGenerated = true)
-@EqualsAndHashCode(includeFields = true)
+@NullCheck
+@EqualsAndHashCode(includeFields = true, callSuper = true)
 final class SimpleCollectionProvider<T> extends AbstractCollectionProvider<T> {
 
     private final Collection<T> ts
 
+    SimpleCollectionProvider(Collection<T> ts) {
+        super([], [])
+        this.ts = ts
+    }
+
     @Override
     Collection<T> provide() {
         this.ts
diff --git a/api/src/main/groovy/com/jessebrault/ssg/provider/SupplierBasedCollectionProvider.groovy b/api/src/main/groovy/com/jessebrault/ssg/provider/SupplierBasedCollectionProvider.groovy
index 8cdbba9..5c2f0a0 100644
--- a/api/src/main/groovy/com/jessebrault/ssg/provider/SupplierBasedCollectionProvider.groovy
+++ b/api/src/main/groovy/com/jessebrault/ssg/provider/SupplierBasedCollectionProvider.groovy
@@ -3,18 +3,29 @@ package com.jessebrault.ssg.provider
 import groovy.transform.EqualsAndHashCode
 import groovy.transform.NullCheck
 import groovy.transform.PackageScope
-import groovy.transform.TupleConstructor
 
 import java.util.function.Supplier
 
 @PackageScope
-@TupleConstructor(defaults = false, includeFields = true)
-@NullCheck(includeGenerated = true)
-@EqualsAndHashCode(includeFields = true)
+@NullCheck
+@EqualsAndHashCode(includeFields = true, callSuper = true)
 final class SupplierBasedCollectionProvider<T> extends AbstractCollectionProvider<T> {
 
     private final Supplier<Collection<T>> supplier
 
+    SupplierBasedCollectionProvider(
+            Collection<CollectionProvider<T>> collectionProviderChildren,
+            Collection<Provider<T>> providerChildren,
+            Supplier<Collection<T>> supplier
+    ) {
+        super(collectionProviderChildren, providerChildren)
+        this.supplier = supplier
+    }
+
+    SupplierBasedCollectionProvider(Supplier<Collection<T>> supplier) {
+        this([], [], supplier)
+    }
+
     @Override
     Collection<T> provide() {
         this.supplier.get()
diff --git a/api/src/test/groovy/com/jessebrault/ssg/buildscript/dsl/AbstractBuildDelegateTests.groovy b/api/src/test/groovy/com/jessebrault/ssg/buildscript/dsl/AbstractBuildDelegateTests.groovy
new file mode 100644
index 0000000..8f19569
--- /dev/null
+++ b/api/src/test/groovy/com/jessebrault/ssg/buildscript/dsl/AbstractBuildDelegateTests.groovy
@@ -0,0 +1,97 @@
+package com.jessebrault.ssg.buildscript.dsl
+
+import com.jessebrault.ssg.SiteSpec
+import com.jessebrault.ssg.buildscript.SourceProviders
+import com.jessebrault.ssg.buildscript.TypesContainer
+import com.jessebrault.ssg.page.Page
+import com.jessebrault.ssg.page.PageTypes
+import com.jessebrault.ssg.provider.CollectionProvider
+import com.jessebrault.ssg.task.TaskFactory
+import com.jessebrault.ssg.text.Text
+import com.jessebrault.ssg.text.TextTypes
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.ExtendWith
+import org.mockito.Mock
+import org.mockito.junit.jupiter.MockitoExtension
+
+import java.util.function.Supplier
+
+import static org.junit.jupiter.api.Assertions.assertEquals
+import static org.junit.jupiter.api.Assertions.assertTrue
+
+@ExtendWith(MockitoExtension)
+abstract class AbstractBuildDelegateTests<T> {
+
+    protected abstract AbstractBuildDelegate<T> getDelegate()
+
+    @Test
+    void siteSpecsAdded() {
+        def d = this.getDelegate()
+        d.siteSpec {
+            name = 'test'
+        }
+        d.siteSpec {
+            baseUrl = 'test'
+        }
+        def sum = d.getSiteSpecResult()
+        assertEquals(new SiteSpec('test', 'test'), sum)
+    }
+
+    @Test
+    void globalsAdded() {
+        def d = this.getDelegate()
+        d.globals {
+            a = 0
+        }
+        d.globals {
+            b = 1
+        }
+        def sum = d.getGlobalsResult()
+        assertEquals([a: 0, b: 1], sum)
+    }
+
+    @Test
+    void typesAdded() {
+        def d = this.getDelegate()
+        d.types {
+            textTypes << TextTypes.MARKDOWN
+        }
+        d.types {
+            pageTypes << PageTypes.GSP
+        }
+        def sum = d.getTypesResult()
+        assertTrue(TextTypes.MARKDOWN in sum.textTypes)
+        assertTrue(PageTypes.GSP in sum.pageTypes)
+    }
+
+    @Test
+    void sourcesAdded(@Mock CollectionProvider<Text> textsProvider, @Mock CollectionProvider<Page> pagesProvider) {
+        def d = this.getDelegate()
+        d.providers {
+            texts(textsProvider)
+        }
+        d.providers {
+            pages(pagesProvider)
+        }
+        def sum = d.getSourcesResult(TypesContainer.getEmpty())
+        assertTrue(textsProvider in sum.textsProvider)
+        assertTrue(pagesProvider in sum.pagesProvider)
+    }
+
+    @Test
+    void taskFactoriesAdded(@Mock Supplier<TaskFactory> taskFactorySupplier) {
+        def d = this.getDelegate()
+        d.taskFactories {
+            register('tf0', taskFactorySupplier)
+        }
+        d.taskFactories {
+            register('tf1', taskFactorySupplier)
+        }
+        def sum = d.getTaskFactoriesResult(SourceProviders.getEmpty())
+        assertEquals(2, sum.size())
+        assertTrue(sum.inject(true) { acc, spec ->
+            acc && spec.supplier == taskFactorySupplier
+        })
+    }
+
+}
diff --git a/api/src/test/groovy/com/jessebrault/ssg/buildscript/dsl/AllBuildsDelegateTests.groovy b/api/src/test/groovy/com/jessebrault/ssg/buildscript/dsl/AllBuildsDelegateTests.groovy
new file mode 100644
index 0000000..6e7b269
--- /dev/null
+++ b/api/src/test/groovy/com/jessebrault/ssg/buildscript/dsl/AllBuildsDelegateTests.groovy
@@ -0,0 +1,12 @@
+package com.jessebrault.ssg.buildscript.dsl
+
+import com.jessebrault.ssg.buildscript.Build
+
+final class AllBuildsDelegateTests extends AbstractBuildDelegateTests<Build.AllBuilds> {
+
+    @Override
+    protected AbstractBuildDelegate<Build.AllBuilds> getDelegate() {
+        new AllBuildsDelegate()
+    }
+
+}
diff --git a/api/src/test/groovy/com/jessebrault/ssg/buildscript/dsl/BuildDelegateTests.groovy b/api/src/test/groovy/com/jessebrault/ssg/buildscript/dsl/BuildDelegateTests.groovy
new file mode 100644
index 0000000..f9063ee
--- /dev/null
+++ b/api/src/test/groovy/com/jessebrault/ssg/buildscript/dsl/BuildDelegateTests.groovy
@@ -0,0 +1,12 @@
+package com.jessebrault.ssg.buildscript.dsl
+
+import com.jessebrault.ssg.buildscript.Build
+
+final class BuildDelegateTests extends AbstractBuildDelegateTests<Build> {
+
+    @Override
+    protected AbstractBuildDelegate<Build> getDelegate() {
+        new BuildDelegate()
+    }
+
+}
diff --git a/api/src/test/groovy/com/jessebrault/ssg/buildscript/dsl/TaskFactoriesDelegateTests.groovy b/api/src/test/groovy/com/jessebrault/ssg/buildscript/dsl/TaskFactoriesDelegateTests.groovy
new file mode 100644
index 0000000..bb7222f
--- /dev/null
+++ b/api/src/test/groovy/com/jessebrault/ssg/buildscript/dsl/TaskFactoriesDelegateTests.groovy
@@ -0,0 +1,49 @@
+package com.jessebrault.ssg.buildscript.dsl
+
+import com.jessebrault.ssg.task.TaskFactory
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.ExtendWith
+import org.junit.jupiter.api.function.Executable
+import org.mockito.Mock
+import org.mockito.junit.jupiter.MockitoExtension
+
+import java.util.function.Consumer
+import java.util.function.Supplier
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow
+import static org.junit.jupiter.api.Assertions.assertEquals
+import static org.junit.jupiter.api.Assertions.assertTrue
+
+@ExtendWith(MockitoExtension)
+final class TaskFactoriesDelegateTests {
+
+    @Test
+    void registerThenConfigure(
+            @Mock Supplier<TaskFactory> taskFactorySupplier,
+            @Mock Consumer<TaskFactory> taskFactoryConsumer
+    ) {
+        def d = new TaskFactoriesDelegate()
+        d.register('test', taskFactorySupplier)
+        assertDoesNotThrow({
+            d.configure('test', TaskFactory, taskFactoryConsumer)
+        } as Executable)
+        def result = d.getResult()
+        assertTrue(result.containsKey('test'))
+        assertEquals(taskFactorySupplier, result['test'].supplier)
+        assertTrue(result['test'].configurators.contains(taskFactoryConsumer))
+    }
+
+    @Test
+    void registerAndConfigure(
+            @Mock Supplier<TaskFactory> taskFactorySupplier,
+            @Mock Consumer<TaskFactory> taskFactoryConsumer
+    ) {
+        def d = new TaskFactoriesDelegate()
+        d.register('test', taskFactorySupplier, taskFactoryConsumer)
+        def result = d.getResult()
+        assertTrue(result.containsKey('test'))
+        assertEquals(taskFactorySupplier, result['test'].supplier)
+        assertTrue(result['test'].configurators.contains(taskFactoryConsumer))
+    }
+
+}