✨ Add minClusterSize to config service

src/services/config-service.js

@@ -21,6 +21,7 @@ import * as output from '../utils/output.js';
 let DEFAULT_CONFIG = {
   comparison: {
     threshold: 2.0,
+    minClusterSize: 2,
   },
   server: {
     port: 47392,
@@ -104,6 +105,13 @@ export function createConfigService({ workingDir }) {
       config.comparison.threshold = parseFloat(process.env.VIZZLY_THRESHOLD);
       sources.comparison = 'env';
     }
+    if (process.env.VIZZLY_MIN_CLUSTER_SIZE) {
+      config.comparison.minClusterSize = parseInt(
+        process.env.VIZZLY_MIN_CLUSTER_SIZE,
+        10
+      );
+      sources.comparison = 'env';
+    }
     if (process.env.VIZZLY_PORT) {
       config.server.port = parseInt(process.env.VIZZLY_PORT, 10);
       sources.server = 'env';
@@ -241,6 +249,20 @@ export default defineConfig(${JSON.stringify(newConfig, null, 2)});
       }
     }
 
+    // Validate minClusterSize
+    if (config.comparison?.minClusterSize !== undefined) {
+      let minClusterSize = config.comparison.minClusterSize;
+      if (!Number.isInteger(minClusterSize) || minClusterSize < 1) {
+        errors.push(
+          'comparison.minClusterSize must be a positive integer (1 or greater)'
+        );
+      } else if (minClusterSize > 100) {
+        warnings.push(
+          'comparison.minClusterSize above 100 may filter out most differences'
+        );
+      }
+    }
+
     // Validate port
     if (config.server?.port !== undefined) {
       let port = config.server.port;

tests/services/config-service.test.js

@@ -43,13 +43,15 @@ describe('services/config-service', () => {
     tempDir = createTempDir();
     // Clear any environment variables that might affect tests
     delete process.env.VIZZLY_THRESHOLD;
+    delete process.env.VIZZLY_MIN_CLUSTER_SIZE;
     delete process.env.VIZZLY_PORT;
   });
 
   afterEach(() => {
     cleanupTempDir(tempDir);
     // Clean up environment variables after each test
     delete process.env.VIZZLY_THRESHOLD;
+    delete process.env.VIZZLY_MIN_CLUSTER_SIZE;
     delete process.env.VIZZLY_PORT;
     delete process.env.VIZZLY_HOME;
   });
@@ -88,6 +90,32 @@ describe('services/config-service', () => {
       assert.strictEqual(config.comparison.threshold, 5.0);
       assert.strictEqual(sources.threshold, 'project');
     });
+
+    it('applies VIZZLY_MIN_CLUSTER_SIZE env var override', async () => {
+      process.env.VIZZLY_MIN_CLUSTER_SIZE = '10';
+
+      let service = createConfigService({ workingDir: tempDir });
+      let { config, sources } = await service.getConfig('merged');
+
+      assert.strictEqual(config.comparison.minClusterSize, 10);
+      assert.strictEqual(sources.comparison, 'env');
+    });
+
+    it('env var overrides project config for minClusterSize', async () => {
+      // Create project config with minClusterSize
+      writeFileSync(
+        join(tempDir, 'vizzly.config.js'),
+        `export default { comparison: { minClusterSize: 3 } };`
+      );
+
+      // Env var should win
+      process.env.VIZZLY_MIN_CLUSTER_SIZE = '8';
+
+      let service = createConfigService({ workingDir: tempDir });
+      let { config } = await service.getConfig('merged');
+
+      assert.strictEqual(config.comparison.minClusterSize, 8);
+    });
   });
 
   describe('getConfig - project', () => {
@@ -334,6 +362,50 @@ describe('services/config-service', () => {
       assert.ok(result.errors.some(e => e.includes('timeout')));
     });
 
+    it('returns error for non-integer minClusterSize', async () => {
+      let service = createConfigService({ workingDir: tempDir });
+
+      let result = await service.validateConfig({
+        comparison: { minClusterSize: 3.5 },
+      });
+
+      assert.strictEqual(result.valid, false);
+      assert.ok(result.errors.some(e => e.includes('minClusterSize')));
+    });
+
+    it('returns error for zero or negative minClusterSize', async () => {
+      let service = createConfigService({ workingDir: tempDir });
+
+      let result = await service.validateConfig({
+        comparison: { minClusterSize: 0 },
+      });
+
+      assert.strictEqual(result.valid, false);
+      assert.ok(result.errors.some(e => e.includes('minClusterSize')));
+    });
+
+    it('returns warning for very high minClusterSize', async () => {
+      let service = createConfigService({ workingDir: tempDir });
+
+      let result = await service.validateConfig({
+        comparison: { minClusterSize: 150 },
+      });
+
+      assert.strictEqual(result.valid, true);
+      assert.ok(result.warnings.some(w => w.includes('100')));
+    });
+
+    it('validates valid minClusterSize', async () => {
+      let service = createConfigService({ workingDir: tempDir });
+
+      let result = await service.validateConfig({
+        comparison: { minClusterSize: 5 },
+      });
+
+      assert.strictEqual(result.valid, true);
+      assert.strictEqual(result.errors.length, 0);
+    });
+
     it('validates empty config as valid', async () => {
       let service = createConfigService({ workingDir: tempDir });