diff --git a/api/src/main/groovy/com/jessebrault/ssg/SiteSpec.groovy b/api/src/main/groovy/com/jessebrault/ssg/SiteSpec.groovy
index 50c29f3..10c248d 100644
--- a/api/src/main/groovy/com/jessebrault/ssg/SiteSpec.groovy
+++ b/api/src/main/groovy/com/jessebrault/ssg/SiteSpec.groovy
@@ -15,8 +15,8 @@ final class SiteSpec {
 
     static SiteSpec concat(SiteSpec s0, SiteSpec s1) {
         new SiteSpec(
-                s0.name.blank ? s1.name : s0.name,
-                s0.baseUrl.blank ? s1.baseUrl : s0.baseUrl
+                s1.name.blank ? s0.name : s1.name,
+                s1.baseUrl.blank ? s0.baseUrl : s1.baseUrl
         )
     }
 
diff --git a/api/src/test/groovy/com/jessebrault/ssg/SiteSpecTests.groovy b/api/src/test/groovy/com/jessebrault/ssg/SiteSpecTests.groovy
index 3f76afd..99dcd64 100644
--- a/api/src/test/groovy/com/jessebrault/ssg/SiteSpecTests.groovy
+++ b/api/src/test/groovy/com/jessebrault/ssg/SiteSpecTests.groovy
@@ -15,11 +15,11 @@ final class SiteSpecTests {
     }
 
     @Test
-    void ifName0NotBlankThenName0() {
+    void ifName1NotBlankThenName1() {
         def ss0 = new SiteSpec('ss0', '')
         def ss1 = new SiteSpec('ss1', '')
         def sum = ss0 + ss1
-        assertEquals('ss0', sum.name)
+        assertEquals('ss1', sum.name)
     }
 
     @Test
@@ -31,11 +31,11 @@ final class SiteSpecTests {
     }
 
     @Test
-    void ifBaseUrl0NotBlankThenBaseUrl0() {
+    void ifBaseUrl1NotBlankThenBaseUrl1() {
         def ss0 = new SiteSpec('', 'ss0')
         def ss1 = new SiteSpec('', 'ss1')
         def sum = ss0 + ss1
-        assertEquals('ss0', sum.baseUrl)
+        assertEquals('ss1', sum.baseUrl)
     }
 
 }
diff --git a/api/src/test/groovy/com/jessebrault/ssg/buildscript/BuildScriptBaseTests.groovy b/api/src/test/groovy/com/jessebrault/ssg/buildscript/BuildScriptBaseTests.groovy
new file mode 100644
index 0000000..d3bbf6b
--- /dev/null
+++ b/api/src/test/groovy/com/jessebrault/ssg/buildscript/BuildScriptBaseTests.groovy
@@ -0,0 +1,143 @@
+package com.jessebrault.ssg.buildscript
+
+import com.jessebrault.ssg.SiteSpec
+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.Function
+
+import static org.junit.jupiter.api.Assertions.assertEquals
+
+@ExtendWith(MockitoExtension)
+final class BuildScriptBaseTests {
+
+    private static Collection<Build> scriptToBuilds(
+            @DelegatesTo(value = BuildScriptBase, strategy = Closure.DELEGATE_FIRST)
+            Closure<?> script
+    ) {
+        def s = new BuildScriptBase() {
+
+            @Override
+            Object run() {
+                script.delegate = this
+                script.resolveStrategy = Closure.DELEGATE_FIRST
+                script()
+            }
+
+        }
+        s.run()
+        s.getBuilds()
+    }
+
+    @Test
+    void oneBuildWithName0() {
+        def r = scriptToBuilds {
+            build('test') { }
+        }
+        assertEquals(1, r.size())
+        def b0 = r[0]
+        assertEquals('test', b0.name)
+    }
+
+    @Test
+    void oneBuildWithName1() {
+        def r = scriptToBuilds {
+            build {
+                name = 'test'
+            }
+        }
+        assertEquals(1, r.size())
+        def b0 = r[0]
+        assertEquals('test', b0.name)
+    }
+
+    @Test
+    void oneBuildOutputDirWithFunction(@Mock Function<Build, OutputDir> mockOutputDirFunction) {
+        def r = scriptToBuilds {
+            build {
+                outputDirFunction = mockOutputDirFunction
+            }
+        }
+        assertEquals(1, r.size())
+        def b0 = r[0]
+        assertEquals(mockOutputDirFunction, b0.outputDirFunction)
+    }
+
+    @Test
+    void oneBuildOutputDirWithFile() {
+        def f = new File('test')
+        def r = scriptToBuilds {
+            build {
+                outputDir = f
+            }
+        }
+        assertEquals(1, r.size())
+        def b0 = r[0]
+        assertEquals(f, b0.outputDirFunction.apply(b0).asFile())
+    }
+
+    @Test
+    void oneBuildOutputDirWithString() {
+        def r = scriptToBuilds {
+            build {
+                outputDir = 'test'
+            }
+        }
+        assertEquals(1, r.size())
+        def b0 = r[0]
+        assertEquals('test', b0.outputDirFunction.apply(b0).path)
+    }
+
+    @Test
+    void oneBuildSiteSpec() {
+        def r = scriptToBuilds {
+            build {
+                siteSpec {
+                    name = 'testSite'
+                    baseUrl = 'https://testsite.com'
+                }
+            }
+        }
+        assertEquals(1, r.size())
+        def b0 = r[0]
+        assertEquals(new SiteSpec('testSite', 'https://testsite.com'), b0.siteSpec)
+    }
+
+    @Test
+    void allBuildsProvidesSiteSpec() {
+        def r = scriptToBuilds {
+            allBuilds {
+                siteSpec {
+                    name = 'testSite'
+                    baseUrl = 'https://testsite.com'
+                }
+            }
+            build('test') { }
+        }
+        assertEquals(1, r.size())
+        def b0 = r[0]
+        assertEquals(new SiteSpec('testSite', 'https://testsite.com'), b0.siteSpec)
+    }
+
+    @Test
+    void allBuildsSiteSpecOverwritten() {
+        def r = scriptToBuilds {
+            allBuilds {
+                siteSpec {
+                    name = 'no'
+                }
+            }
+            build {
+                siteSpec {
+                    name = 'yes'
+                }
+            }
+        }
+        assertEquals(1, r.size())
+        def b0 = r[0]
+        assertEquals(new SiteSpec('yes', ''), b0.siteSpec)
+    }
+
+}