Add command for updating snapshots in watch mode

api.js

@@ -60,6 +60,10 @@ class Api extends EventEmitter {
 		precompiled[resolvedfpath] = hash;
 
 		const options = Object.assign({}, this.options, {precompiled});
+		if (runStatus.updateSnapshots) {
+			// Don't use in Object.assign() since it'll override options.updateSnapshots even when false.
+			options.updateSnapshots = true;
+		}
 		const emitter = fork(file, options, execArgv);
 		runStatus.observeFork(emitter);
 
@@ -137,7 +141,8 @@ class Api extends EventEmitter {
 			runOnlyExclusive: options.runOnlyExclusive,
 			prefixTitles: this.options.explicitTitles || files.length > 1,
 			base: path.relative(process.cwd(), commonPathPrefix(files)) + path.sep,
-			failFast: this.options.failFast
+			failFast: this.options.failFast,
+			updateSnapshots: options.updateSnapshots
 		});
 
 		this.emit('test-run', runStatus, files);

docs/recipes/watch-mode.md

@@ -91,6 +91,10 @@ If you run AVA in your CI with watch mode, the execution will exit with an error
 
 You can quickly rerun all tests by typing <kbd>r</kbd> on the console, followed by <kbd>Enter</kbd>.
 
+## Updating snapshots
+
+You can update failing snapshots by typing <kbd>u</kbd> on the console, followed by <kbd>Enter</kbd>.
+
 ## Debugging
 
 Sometimes watch mode does something surprising like rerunning all tests when you thought only a single test would be run. To see its reasoning you can enable a debug mode. This will work best with the verbose reporter:

lib/run-status.js

@@ -40,6 +40,7 @@ class RunStatus extends EventEmitter {
 		this.stats = [];
 		this.tests = [];
 		this.failFastEnabled = opts.failFast || false;
+		this.updateSnapshots = opts.updateSnapshots || false;
 
 		autoBind(this);
 	}

lib/watcher.js

@@ -84,7 +84,8 @@ class Watcher {
 
 		this.clearLogOnNextRun = true;
 		this.runVector = 0;
-		this.run = specificFiles => {
+		this.previousFiles = files;
+		this.run = (specificFiles, updateSnapshots) => {
 			if (this.runVector > 0) {
 				const cleared = this.clearLogOnNextRun && logger.clear();
 				if (!cleared) {
@@ -117,7 +118,8 @@ class Watcher {
 			}
 
 			this.touchedFiles.clear();
-			this.busy = api.run(specificFiles || files, {runOnlyExclusive})
+			this.previousFiles = specificFiles || files;
+			this.busy = api.run(this.previousFiles, {runOnlyExclusive, updateSnapshots: updateSnapshots === true})
 				.then(runStatus => {
 					runStatus.previousFailCount = this.sumPreviousFailures(currentVector);
 					logger.finish(runStatus);
@@ -273,7 +275,7 @@ class Watcher {
 
 		stdin.on('data', data => {
 			data = data.trim().toLowerCase();
-			if (data !== 'r' && data !== 'rs') {
+			if (data !== 'r' && data !== 'rs' && data !== 'u') {
 				return;
 			}
 
@@ -285,14 +287,22 @@ class Watcher {
 				// the busy promise to fulfil
 				this.debouncer.cancel();
 				this.clearLogOnNextRun = false;
-				this.rerunAll();
+				if (data === 'u') {
+					this.updatePreviousSnapshots();
+				} else {
+					this.rerunAll();
+				}
 			});
 		});
 	}
 	rerunAll() {
 		this.dirtyStates = {};
 		this.run();
 	}
+	updatePreviousSnapshots() {
+		this.dirtyStates = {};
+		this.run(this.previousFiles, true);
+	}
 	runAfterChanges() {
 		const dirtyStates = this.dirtyStates;
 		this.dirtyStates = {};