diff --git a/packages/build/build/build.js b/packages/build/build/build.js
index 494499d..0ffc183 100644
--- a/packages/build/build/build.js
+++ b/packages/build/build/build.js
@@ -44,7 +44,12 @@ module.exports = class Build extends Flecks {
       .filter((e) => e);
   }
 
-  static async buildRuntime(originalConfig, platforms, flecks = {}) {
+  static async buildRuntime({
+    flecks = {},
+    originalConfig,
+    platforms,
+    root,
+  }) {
     const cleanConfig = JSON.parse(JSON.stringify(originalConfig));
     // Dealias the config keys.
     const dealiasedConfig = Object.fromEntries(
@@ -57,7 +62,7 @@ module.exports = class Build extends Flecks {
           ];
         }),
     );
-    const resolver = new Resolver({root: FLECKS_CORE_ROOT});
+    const resolver = new Resolver({root});
     const {paths, roots} = await explicate({
       paths: Object.keys(originalConfig),
       platforms,
@@ -129,6 +134,7 @@ module.exports = class Build extends Flecks {
       config: configParameter,
       flecks: configFlecks,
       platforms = ['server'],
+      root = FLECKS_CORE_ROOT,
     } = {},
   ) {
     // Load or use parameterized configuration.
@@ -136,7 +142,7 @@ module.exports = class Build extends Flecks {
     let configType = 'parameter';
     if (!configParameter) {
       // eslint-disable-next-line no-param-reassign
-      [configType, originalConfig] = await loadConfig();
+      [configType, originalConfig] = await loadConfig(root);
     }
     else {
       originalConfig = JSON.parse(JSON.stringify(configParameter));
@@ -147,9 +153,15 @@ module.exports = class Build extends Flecks {
       resolver,
       roots,
       runtime,
-    } = await this.buildRuntime(originalConfig, platforms, configFlecks);
+    } = await this.buildRuntime({
+      flecks: configFlecks,
+      originalConfig,
+      platforms,
+      root,
+    });
     const flecks = await super.from(runtime);
     flecks.platforms = platforms;
+    flecks.root = root;
     flecks.roots = roots;
     flecks.resolver = resolver;
     flecks.loadBuildFiles();
@@ -181,7 +193,7 @@ module.exports = class Build extends Flecks {
     if (!fleck) {
       throw new Error(`Unknown build config: '${config}'`);
     }
-    const rootConfig = await this.resolver.resolve(join(FLECKS_CORE_ROOT, 'build', config));
+    const rootConfig = await this.resolver.resolve(join(this.root, 'build', config));
     if (rootConfig) {
       return rootConfig;
     }
diff --git a/packages/build/build/load-config.js b/packages/build/build/load-config.js
index a339c4b..a5a75e8 100644
--- a/packages/build/build/load-config.js
+++ b/packages/build/build/load-config.js
@@ -5,14 +5,10 @@ const D = require('@flecks/core/build/debug');
 
 const debug = D('@flecks/build/build/load-config');
 
-const {
-  FLECKS_CORE_ROOT = process.cwd(),
-} = process.env;
-
-module.exports = async function loadConfig() {
+module.exports = async function loadConfig(root) {
   try {
     const {load} = require('js-yaml');
-    const filename = join(FLECKS_CORE_ROOT, 'build', 'flecks.yml');
+    const filename = join(root, 'build', 'flecks.yml');
     const buffer = await readFile(filename, 'utf8');
     debug('parsing configuration from YML...');
     return ['YML', load(buffer, {filename})];
@@ -21,7 +17,7 @@ module.exports = async function loadConfig() {
     if ('ENOENT' !== error.code) {
       throw error;
     }
-    const {name} = require(join(FLECKS_CORE_ROOT, 'package.json'));
+    const {name} = require(join(root, 'package.json'));
     const barebones = {
       '@flecks/build': {},
       '@flecks/core': {},
@@ -30,7 +26,7 @@ module.exports = async function loadConfig() {
     if (barebones[name]) {
       delete barebones[name];
     }
-    barebones[`${name}:${FLECKS_CORE_ROOT}`] = {};
+    barebones[`${name}:${root}`] = {};
     return ['barebones', barebones];
   }
 };
diff --git a/packages/build/package.json b/packages/build/package.json
index 133c74f..0b050ca 100644
--- a/packages/build/package.json
+++ b/packages/build/package.json
@@ -11,7 +11,7 @@
     "clean": "rm -rf dist node_modules yarn.lock",
     "lint": "eslint --config ./build/eslint.config.js .",
     "postversion": "npm run build",
-    "test": "webpack --config ../core/build/build.test.webpack.config.js --mode production && mocha --colors ./dist/test.js --timeout 10000",
+    "test": "webpack --config ./build/build.test.webpack.config.js --mode production && mocha --colors ./dist/test.js --timeout 10000",
     "test:watch": "webpack watch --config ./build/build.test.webpack.config.js --mode development & mocha --parallel --watch --watch-files ./dist/test.js --colors ./dist/test.js --timeout 10000"
   },
   "bin": {
diff --git a/packages/build/test/server/build.js b/packages/build/test/server/build.js
new file mode 100644
index 0000000..d409947
--- /dev/null
+++ b/packages/build/test/server/build.js
@@ -0,0 +1,56 @@
+import {join} from 'path';
+
+import {expect} from 'chai';
+
+const {
+  FLECKS_CORE_ROOT = process.cwd(),
+} = process.env;
+
+const Build = __non_webpack_require__(join(FLECKS_CORE_ROOT, 'build', 'build'));
+const loadConfig = __non_webpack_require__(join(FLECKS_CORE_ROOT, 'build', 'load-config'));
+
+const buildRoot = join(FLECKS_CORE_ROOT, 'test', 'server', 'build', 'root');
+
+it('defaults config', async () => {
+  expect(await loadConfig(FLECKS_CORE_ROOT))
+    .to.deep.equal([
+      'barebones',
+      {
+        [`@flecks/build:${FLECKS_CORE_ROOT}`]: {},
+        '@flecks/core': {},
+        '@flecks/fleck': {},
+      },
+    ]);
+});
+
+it('loads config', async () => {
+  expect(await loadConfig(buildRoot))
+    .to.deep.equal(['YML', {one: {}, 'two:./two': {}}]);
+});
+
+it('configures from environment', async () => {
+  const {env} = process;
+  env.FLECKS_ENV__one__foo = '{"boo": 2}';
+  env.FLECKS_ENV__two__bar = 'yo';
+  expect(
+    Build.environmentConfiguration({
+      one: {foo: {boo: 1}},
+      two: {bar: 'hi'},
+    }),
+  )
+    .to.deep.equal({
+      one: {foo: {boo: 2}},
+      two: {bar: 'yo'},
+    });
+});
+
+it('dealiases config', async () => {
+  expect(await Build.buildRuntime({
+    originalConfig: {'two:./two': {foo: 2}},
+    platforms: [],
+    root: buildRoot,
+  }))
+    .to.nested.include({
+      'runtime.config.two.foo': 2,
+    });
+});
diff --git a/packages/build/test/server/build/root/build/flecks.yml b/packages/build/test/server/build/root/build/flecks.yml
new file mode 100644
index 0000000..457610c
--- /dev/null
+++ b/packages/build/test/server/build/root/build/flecks.yml
@@ -0,0 +1,2 @@
+one: {}
+'two:./two': {}
\ No newline at end of file
diff --git a/packages/build/test/server/build/root/two/index.js b/packages/build/test/server/build/root/two/index.js
new file mode 100644
index 0000000..e69de29
diff --git a/packages/build/test/server/build/root/two/package.json b/packages/build/test/server/build/root/two/package.json
new file mode 100644
index 0000000..9e26dfe
--- /dev/null
+++ b/packages/build/test/server/build/root/two/package.json
@@ -0,0 +1 @@
+{}
\ No newline at end of file
diff --git a/packages/build/test/server/yml/build/flecks.yml b/packages/build/test/server/yml/build/flecks.yml
new file mode 100644
index 0000000..2d1adf9
--- /dev/null
+++ b/packages/build/test/server/yml/build/flecks.yml
@@ -0,0 +1,4 @@
+a: {}
+bar: {}
+foo: {}
+two: {}