diff --git a/doc/api/v8.md b/doc/api/v8.md
index 921c4378199496..7af37fba947e78 100644
--- a/doc/api/v8.md
+++ b/doc/api/v8.md
@@ -214,6 +214,32 @@ v8.setFlagsFromString('--trace_gc');
 setTimeout(() => { v8.setFlagsFromString('--notrace_gc'); }, 60e3);
 ```
 
+## `v8.takeCoverage()`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+The `v8.takeCoverage()` method allows the user to write the coverage started by
+[`NODE_V8_COVERAGE`][] to disk on demand. This method can be invoked multiple
+times during the lifetime of the process, each time the execution counter will
+be reset and a new coverage report will be written to the directory specified
+by [`NODE_V8_COVERAGE`][].
+
+When the process is about to exit, one last coverage will still be written to
+disk, unless [`v8.stopCoverage()`][] is invoked before the process exits.
+
+## `v8.stopCoverage()`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+The `v8.stopCoverage()` method allows the user to stop the coverage collection
+started by [`NODE_V8_COVERAGE`][], so that V8 can release the execution count
+records and optimize code. This can be used in conjunction with
+`v8.takeCoverage()` if the user wants to collect the coverage on demand.
+
 ## `v8.writeHeapSnapshot([filename])`
 <!-- YAML
 added: v11.13.0
@@ -509,6 +535,7 @@ A subclass of [`Deserializer`][] corresponding to the format written by
 [`Deserializer`]: #v8_class_v8_deserializer
 [`Error`]: errors.html#errors_class_error
 [`GetHeapSpaceStatistics`]: https://v8docs.nodesource.com/node-13.2/d5/dda/classv8_1_1_isolate.html#ac673576f24fdc7a33378f8f57e1d13a4
+[`NODE_V8_COVERAGE`]: cli.md#cli_node_v8_coverage_dir
 [`Serializer`]: #v8_class_v8_serializer
 [`deserializer._readHostObject()`]: #v8_deserializer_readhostobject
 [`deserializer.transferArrayBuffer()`]: #v8_deserializer_transferarraybuffer_id_arraybuffer
@@ -518,6 +545,7 @@ A subclass of [`Deserializer`][] corresponding to the format written by
 [`serializer.releaseBuffer()`]: #v8_serializer_releasebuffer
 [`serializer.transferArrayBuffer()`]: #v8_serializer_transferarraybuffer_id_arraybuffer
 [`serializer.writeRawBytes()`]: #v8_serializer_writerawbytes_buffer
+[`v8.stopCoverage()`]: #v8_v8_stopcoverage
 [`vm.Script`]: vm.html#vm_new_vm_script_code_options
 [HTML structured clone algorithm]: https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm
 [V8]: https://developers.google.com/v8/
diff --git a/lib/v8.js b/lib/v8.js
index fe848dad72a15c..2143e07274775d 100644
--- a/lib/v8.js
+++ b/lib/v8.js
@@ -37,6 +37,12 @@ const {
   Serializer: _Serializer,
   Deserializer: _Deserializer
 } = internalBinding('serdes');
+
+let profiler = {};
+if (internalBinding('config').hasInspector) {
+  profiler = internalBinding('profiler');
+}
+
 const assert = require('internal/assert');
 const { copy } = internalBinding('buffer');
 const { inspect } = require('internal/util/inspect');
@@ -286,6 +292,8 @@ module.exports = {
   DefaultSerializer,
   DefaultDeserializer,
   deserialize,
+  takeCoverage: profiler.takeCoverage,
+  stopCoverage: profiler.stopCoverage,
   serialize,
   writeHeapSnapshot,
 };
diff --git a/src/inspector_profiler.cc b/src/inspector_profiler.cc
index 03cf2f6e5ca76b..7640a040783b85 100644
--- a/src/inspector_profiler.cc
+++ b/src/inspector_profiler.cc
@@ -9,6 +9,7 @@
 #include "util-inl.h"
 #include "v8-inspector.h"
 
+#include <cinttypes>
 #include <sstream>
 
 namespace node {
@@ -36,10 +37,11 @@ V8ProfilerConnection::V8ProfilerConnection(Environment* env)
           false)),
       env_(env) {}
 
-size_t V8ProfilerConnection::DispatchMessage(const char* method,
-                                             const char* params) {
+uint32_t V8ProfilerConnection::DispatchMessage(const char* method,
+                                               const char* params,
+                                               bool is_profile_request) {
   std::stringstream ss;
-  size_t id = next_id();
+  uint32_t id = next_id();
   ss << R"({ "id": )" << id;
   DCHECK(method != nullptr);
   ss << R"(, "method": ")" << method << '"';
@@ -50,12 +52,15 @@ size_t V8ProfilerConnection::DispatchMessage(const char* method,
   std::string message = ss.str();
   const uint8_t* message_data =
       reinterpret_cast<const uint8_t*>(message.c_str());
+  // Save the id of the profile request to identify its response.
+  if (is_profile_request) {
+    profile_ids_.insert(id);
+  }
   Debug(env(),
         DebugCategory::INSPECTOR_PROFILER,
         "Dispatching message %s\n",
         message.c_str());
   session_->Dispatch(StringView(message_data, message.length()));
-  // TODO(joyeecheung): use this to identify the ending message.
   return id;
 }
 
@@ -77,21 +82,10 @@ void V8ProfilerConnection::V8ProfilerSessionDelegate::SendMessageToFrontend(
   Environment* env = connection_->env();
   Isolate* isolate = env->isolate();
   HandleScope handle_scope(isolate);
-  Context::Scope context_scope(env->context());
+  Local<Context> context = env->context();
+  Context::Scope context_scope(context);
 
-  // TODO(joyeecheung): always parse the message so that we can use the id to
-  // identify ending messages as well as printing the message in the debug
-  // output when there is an error.
   const char* type = connection_->type();
-  Debug(env,
-        DebugCategory::INSPECTOR_PROFILER,
-        "Receive %s profile message, ending = %s\n",
-        type,
-        connection_->ending() ? "true" : "false");
-  if (!connection_->ending()) {
-    return;
-  }
-
   // Convert StringView to a Local<String>.
   Local<String> message_str;
   if (!String::NewFromTwoByte(isolate,
@@ -99,11 +93,62 @@ void V8ProfilerConnection::V8ProfilerSessionDelegate::SendMessageToFrontend(
                               NewStringType::kNormal,
                               message.length())
            .ToLocal(&message_str)) {
-    fprintf(stderr, "Failed to convert %s profile message\n", type);
+    fprintf(
+        stderr, "Failed to convert %s profile message to V8 string\n", type);
+    return;
+  }
+
+  Debug(env,
+        DebugCategory::INSPECTOR_PROFILER,
+        "Receive %s profile message\n",
+        type);
+
+  Local<Value> parsed;
+  if (!v8::JSON::Parse(context, message_str).ToLocal(&parsed) ||
+      !parsed->IsObject()) {
+    fprintf(stderr, "Failed to parse %s profile result as JSON object\n", type);
+    return;
+  }
+
+  Local<Object> response = parsed.As<Object>();
+  Local<Value> id_v;
+  if (!response->Get(context, FIXED_ONE_BYTE_STRING(isolate, "id"))
+           .ToLocal(&id_v) ||
+      !id_v->IsUint32()) {
+    Utf8Value str(isolate, message_str);
+    fprintf(
+        stderr, "Cannot retrieve id from the response message:\n%s\n", *str);
     return;
   }
+  uint32_t id = id_v.As<v8::Uint32>()->Value();
 
-  connection_->WriteProfile(message_str);
+  if (!connection_->HasProfileId(id)) {
+    Utf8Value str(isolate, message_str);
+    Debug(env, DebugCategory::INSPECTOR_PROFILER, "%s\n", *str);
+    return;
+  } else {
+    Debug(env,
+          DebugCategory::INSPECTOR_PROFILER,
+          "Writing profile response (id = %" PRIu64 ")\n",
+          static_cast<uint64_t>(id));
+  }
+
+  // Get message.result from the response.
+  Local<Value> result_v;
+  if (!response->Get(context, FIXED_ONE_BYTE_STRING(isolate, "result"))
+           .ToLocal(&result_v)) {
+    fprintf(stderr, "Failed to get 'result' from %s profile response\n", type);
+    return;
+  }
+
+  if (!result_v->IsObject()) {
+    fprintf(
+        stderr, "'result' from %s profile response is not an object\n", type);
+    return;
+  }
+
+  connection_->WriteProfile(result_v.As<Object>());
+  connection_->RemoveProfileId(id);
 }
 
 static bool EnsureDirectory(const std::string& directory, const char* type) {
@@ -138,45 +183,9 @@ std::string V8CoverageConnection::GetFilename() const {
   return filename;
 }
 
-static MaybeLocal<Object> ParseProfile(Environment* env,
-                                       Local<String> message,
-                                       const char* type) {
-  Local<Context> context = env->context();
-  Isolate* isolate = env->isolate();
-
-  // Get message.result from the response
-  Local<Value> parsed;
-  if (!v8::JSON::Parse(context, message).ToLocal(&parsed) ||
-      !parsed->IsObject()) {
-    fprintf(stderr, "Failed to parse %s profile result as JSON object\n", type);
-    return MaybeLocal<Object>();
-  }
-
-  Local<Value> result_v;
-  if (!parsed.As<Object>()
-           ->Get(context, FIXED_ONE_BYTE_STRING(isolate, "result"))
-           .ToLocal(&result_v)) {
-    fprintf(stderr, "Failed to get 'result' from %s profile message\n", type);
-    return MaybeLocal<Object>();
-  }
-
-  if (!result_v->IsObject()) {
-    fprintf(
-        stderr, "'result' from %s profile message is not an object\n", type);
-    return MaybeLocal<Object>();
-  }
-
-  return result_v.As<Object>();
-}
-
-void V8ProfilerConnection::WriteProfile(Local<String> message) {
+void V8ProfilerConnection::WriteProfile(Local<Object> result) {
   Local<Context> context = env_->context();
 
-  // Get message.result from the response.
-  Local<Object> result;
-  if (!ParseProfile(env_, message, type()).ToLocal(&result)) {
-    return;
-  }
   // Generate the profile output from the subclass.
   Local<Object> profile;
   if (!GetProfile(result).ToLocal(&profile)) {
@@ -203,7 +212,7 @@ void V8ProfilerConnection::WriteProfile(Local<String> message) {
   WriteResult(env_, path.c_str(), result_s);
 }
 
-void V8CoverageConnection::WriteProfile(Local<String> message) {
+void V8CoverageConnection::WriteProfile(Local<Object> result) {
   Isolate* isolate = env_->isolate();
   Local<Context> context = env_->context();
   HandleScope handle_scope(isolate);
@@ -219,11 +228,6 @@ void V8CoverageConnection::WriteProfile(Local<String> message) {
     return;
   }
 
-  // Get message.result from the response.
-  Local<Object> result;
-  if (!ParseProfile(env_, message, type()).ToLocal(&result)) {
-    return;
-  }
   // Generate the profile output from the subclass.
   Local<Object> profile;
   if (!GetProfile(result).ToLocal(&profile)) {
@@ -287,10 +291,23 @@ void V8CoverageConnection::Start() {
                   R"({ "callCount": true, "detailed": true })");
 }
 
+void V8CoverageConnection::TakeCoverage() {
+  DispatchMessage("Profiler.takePreciseCoverage", nullptr, true);
+}
+
+void V8CoverageConnection::StopCoverage() {
+  DispatchMessage("Profiler.stopPreciseCoverage");
+}
+
 void V8CoverageConnection::End() {
-  CHECK_EQ(ending_, false);
+  Debug(env_,
+      DebugCategory::INSPECTOR_PROFILER,
+      "V8CoverageConnection::End(), ending = %d\n", ending_);
+  if (ending_) {
+    return;
+  }
   ending_ = true;
-  DispatchMessage("Profiler.takePreciseCoverage");
+  TakeCoverage();
 }
 
 std::string V8CpuProfilerConnection::GetDirectory() const {
@@ -327,9 +344,14 @@ void V8CpuProfilerConnection::Start() {
 }
 
 void V8CpuProfilerConnection::End() {
-  CHECK_EQ(ending_, false);
+  Debug(env_,
+      DebugCategory::INSPECTOR_PROFILER,
+      "V8CpuProfilerConnection::End(), ending = %d\n", ending_);
+  if (ending_) {
+    return;
+  }
   ending_ = true;
-  DispatchMessage("Profiler.stop");
+  DispatchMessage("Profiler.stop", nullptr, true);
 }
 
 std::string V8HeapProfilerConnection::GetDirectory() const {
@@ -365,31 +387,33 @@ void V8HeapProfilerConnection::Start() {
 }
 
 void V8HeapProfilerConnection::End() {
-  CHECK_EQ(ending_, false);
+  Debug(env_,
+      DebugCategory::INSPECTOR_PROFILER,
+      "V8HeapProfilerConnection::End(), ending = %d\n", ending_);
+  if (ending_) {
+    return;
+  }
   ending_ = true;
-  DispatchMessage("HeapProfiler.stopSampling");
+  DispatchMessage("HeapProfiler.stopSampling", nullptr, true);
 }
 
 // For now, we only support coverage profiling, but we may add more
 // in the future.
 static void EndStartedProfilers(Environment* env) {
+  // TODO(joyeechueng): merge these connections and use one session per env.
   Debug(env, DebugCategory::INSPECTOR_PROFILER, "EndStartedProfilers\n");
   V8ProfilerConnection* connection = env->cpu_profiler_connection();
-  if (connection != nullptr && !connection->ending()) {
-    Debug(env, DebugCategory::INSPECTOR_PROFILER, "Ending cpu profiling\n");
+  if (connection != nullptr) {
     connection->End();
   }
 
   connection = env->heap_profiler_connection();
-  if (connection != nullptr && !connection->ending()) {
-    Debug(env, DebugCategory::INSPECTOR_PROFILER, "Ending heap profiling\n");
+  if (connection != nullptr) {
     connection->End();
   }
 
   connection = env->coverage_connection();
-  if (connection != nullptr && !connection->ending()) {
-    Debug(
-        env, DebugCategory::INSPECTOR_PROFILER, "Ending coverage collection\n");
+  if (connection != nullptr) {
     connection->End();
   }
 }
@@ -469,6 +493,37 @@ static void SetSourceMapCacheGetter(const FunctionCallbackInfo<Value>& args) {
   env->set_source_map_cache_getter(args[0].As<Function>());
 }
 
+static void TakeCoverage(const FunctionCallbackInfo<Value>& args) {
+  Environment* env = Environment::GetCurrent(args);
+  V8CoverageConnection* connection = env->coverage_connection();
+
+  Debug(
+    env,
+    DebugCategory::INSPECTOR_PROFILER,
+    "TakeCoverage, connection %s nullptr\n",
+    connection == nullptr ? "==" : "!=");
+
+  if (connection != nullptr) {
+    Debug(env, DebugCategory::INSPECTOR_PROFILER, "taking coverage\n");
+    connection->TakeCoverage();
+  }
+}
+
+static void StopCoverage(const FunctionCallbackInfo<Value>& args) {
+  Environment* env = Environment::GetCurrent(args);
+  V8CoverageConnection* connection = env->coverage_connection();
+
+  Debug(env,
+        DebugCategory::INSPECTOR_PROFILER,
+        "StopCoverage, connection %s nullptr\n",
+        connection == nullptr ? "==" : "!=");
+
+  if (connection != nullptr) {
+    Debug(env, DebugCategory::INSPECTOR_PROFILER, "Stopping coverage\n");
+    connection->StopCoverage();
+  }
+}
+
 static void Initialize(Local<Object> target,
                        Local<Value> unused,
                        Local<Context> context,
@@ -476,6 +531,8 @@ static void Initialize(Local<Object> target,
   Environment* env = Environment::GetCurrent(context);
   env->SetMethod(target, "setCoverageDirectory", SetCoverageDirectory);
   env->SetMethod(target, "setSourceMapCacheGetter", SetSourceMapCacheGetter);
+  env->SetMethod(target, "takeCoverage", TakeCoverage);
+  env->SetMethod(target, "stopCoverage", StopCoverage);
 }
 
 }  // namespace profiler
diff --git a/src/inspector_profiler.h b/src/inspector_profiler.h
index 187bc0d1c49a16..be74153b0c37ac 100644
--- a/src/inspector_profiler.h
+++ b/src/inspector_profiler.h
@@ -7,6 +7,7 @@
 #error("This header can only be used when inspector is enabled")
 #endif
 
+#include <unordered_set>
 #include "inspector_agent.h"
 
 namespace node {
@@ -39,7 +40,9 @@ class V8ProfilerConnection {
   // The optional `params` should be formatted in JSON.
   // The strings should be in one byte characters - which is enough for
   // the commands we use here.
-  size_t DispatchMessage(const char* method, const char* params = nullptr);
+  uint32_t DispatchMessage(const char* method,
+                           const char* params = nullptr,
+                           bool is_profile_request = false);
 
   // Use DispatchMessage() to dispatch necessary inspector messages
   // to start and end the profiling.
@@ -58,12 +61,19 @@ class V8ProfilerConnection {
   // which will be then written as a JSON.
   virtual v8::MaybeLocal<v8::Object> GetProfile(
       v8::Local<v8::Object> result) = 0;
-  virtual void WriteProfile(v8::Local<v8::String> message);
+  virtual void WriteProfile(v8::Local<v8::Object> result);
+
+  bool HasProfileId(uint32_t id) const {
+    return profile_ids_.find(id) != profile_ids_.end();
+  }
+
+  void RemoveProfileId(uint32_t id) { profile_ids_.erase(id); }
 
  private:
-  size_t next_id() { return id_++; }
+  uint32_t next_id() { return id_++; }
   std::unique_ptr<inspector::InspectorSession> session_;
-  size_t id_ = 1;
+  uint32_t id_ = 1;
+  std::unordered_set<uint32_t> profile_ids_;
 
  protected:
   Environment* env_ = nullptr;
@@ -82,8 +92,10 @@ class V8CoverageConnection : public V8ProfilerConnection {
   std::string GetDirectory() const override;
   std::string GetFilename() const override;
   v8::MaybeLocal<v8::Object> GetProfile(v8::Local<v8::Object> result) override;
-  void WriteProfile(v8::Local<v8::String> message) override;
+  void WriteProfile(v8::Local<v8::Object> result) override;
   void WriteSourceMapCache();
+  void TakeCoverage();
+  void StopCoverage();
 
  private:
   std::unique_ptr<inspector::InspectorSession> session_;
diff --git a/test/fixtures/v8-coverage/interval.js b/test/fixtures/v8-coverage/interval.js
new file mode 100644
index 00000000000000..8fb10cef64ddb8
--- /dev/null
+++ b/test/fixtures/v8-coverage/interval.js
@@ -0,0 +1,14 @@
+'use strict';
+let counter = 0;
+let result;
+const TEST_INTERVALS = parseInt(process.env.TEST_INTERVALS) || 1;
+
+const i = setInterval(function interval() {
+  counter++;
+  if (counter < TEST_INTERVALS) {
+    result = 1;
+  } else {
+    result = process.hrtime();
+    clearInterval(i);
+  }
+}, 100);
diff --git a/test/fixtures/v8-coverage/stop-coverage.js b/test/fixtures/v8-coverage/stop-coverage.js
new file mode 100644
index 00000000000000..dadfd1900bdd78
--- /dev/null
+++ b/test/fixtures/v8-coverage/stop-coverage.js
@@ -0,0 +1,3 @@
+'use strict';
+const v8 = require('v8');
+v8.stopCoverage();
diff --git a/test/fixtures/v8-coverage/take-coverage.js b/test/fixtures/v8-coverage/take-coverage.js
new file mode 100644
index 00000000000000..766c1f400747a8
--- /dev/null
+++ b/test/fixtures/v8-coverage/take-coverage.js
@@ -0,0 +1,10 @@
+'use strict';
+const v8 = require('v8');
+
+setTimeout(() => {
+  v8.takeCoverage();
+}, 1000);
+
+setTimeout(() => {
+  v8.takeCoverage();
+}, 2000);
diff --git a/test/parallel/test-v8-stop-coverage.js b/test/parallel/test-v8-stop-coverage.js
new file mode 100644
index 00000000000000..020e18d8747eb2
--- /dev/null
+++ b/test/parallel/test-v8-stop-coverage.js
@@ -0,0 +1,34 @@
+'use strict';
+
+if (!process.features.inspector) return;
+
+require('../common');
+const fixtures = require('../common/fixtures');
+const tmpdir = require('../common/tmpdir');
+const assert = require('assert');
+const fs = require('fs');
+const { spawnSync } = require('child_process');
+
+tmpdir.refresh();
+const intervals = 20;
+
+{
+  const output = spawnSync(process.execPath, [
+    '-r',
+    fixtures.path('v8-coverage', 'stop-coverage'),
+    '-r',
+    fixtures.path('v8-coverage', 'take-coverage'),
+    fixtures.path('v8-coverage', 'interval'),
+  ], {
+    env: {
+      ...process.env,
+      NODE_V8_COVERAGE: tmpdir.path,
+      NODE_DEBUG_NATIVE: 'INSPECTOR_PROFILER',
+      TEST_INTERVALS: intervals
+    },
+  });
+  console.log(output.stderr.toString());
+  assert.strictEqual(output.status, 0);
+  const coverageFiles = fs.readdirSync(tmpdir.path);
+  assert.strictEqual(coverageFiles.length, 0);
+}
diff --git a/test/parallel/test-v8-take-coverage-noop.js b/test/parallel/test-v8-take-coverage-noop.js
new file mode 100644
index 00000000000000..c1c797bfd42220
--- /dev/null
+++ b/test/parallel/test-v8-take-coverage-noop.js
@@ -0,0 +1,32 @@
+'use strict';
+
+if (!process.features.inspector) return;
+
+require('../common');
+const fixtures = require('../common/fixtures');
+const tmpdir = require('../common/tmpdir');
+const assert = require('assert');
+const fs = require('fs');
+const { spawnSync } = require('child_process');
+
+tmpdir.refresh();
+
+// v8.takeCoverage() should be a noop if NODE_V8_COVERAGE is not set.
+const intervals = 40;
+{
+  const output = spawnSync(process.execPath, [
+    '-r',
+    fixtures.path('v8-coverage', 'take-coverage'),
+    fixtures.path('v8-coverage', 'interval'),
+  ], {
+    env: {
+      ...process.env,
+      NODE_DEBUG_NATIVE: 'INSPECTOR_PROFILER',
+      TEST_INTERVALS: intervals
+    },
+  });
+  console.log(output.stderr.toString());
+  assert.strictEqual(output.status, 0);
+  const coverageFiles = fs.readdirSync(tmpdir.path);
+  assert.strictEqual(coverageFiles.length, 0);
+}
diff --git a/test/parallel/test-v8-take-coverage.js b/test/parallel/test-v8-take-coverage.js
new file mode 100644
index 00000000000000..b5e99ac30a5717
--- /dev/null
+++ b/test/parallel/test-v8-take-coverage.js
@@ -0,0 +1,85 @@
+'use strict';
+
+if (!process.features.inspector) return;
+
+require('../common');
+const fixtures = require('../common/fixtures');
+const tmpdir = require('../common/tmpdir');
+const assert = require('assert');
+const fs = require('fs');
+const path = require('path');
+const { spawnSync } = require('child_process');
+
+tmpdir.refresh();
+const intervals = 40;
+// Outputs coverage when v8.takeCoverage() is invoked.
+{
+  const output = spawnSync(process.execPath, [
+    '-r',
+    fixtures.path('v8-coverage', 'take-coverage'),
+    fixtures.path('v8-coverage', 'interval'),
+  ], {
+    env: {
+      ...process.env,
+      NODE_V8_COVERAGE: tmpdir.path,
+      NODE_DEBUG_NATIVE: 'INSPECTOR_PROFILER',
+      TEST_INTERVALS: intervals
+    },
+  });
+  console.log(output.stderr.toString());
+  assert.strictEqual(output.status, 0);
+  const coverageFiles = fs.readdirSync(tmpdir.path);
+
+  let coverages = [];
+  for (const coverageFile of coverageFiles) {
+    const coverage = require(path.join(tmpdir.path, coverageFile));
+    for (const result of coverage.result) {
+      if (result.url.includes('/interval')) {
+        coverages.push({
+          file: coverageFile,
+          func: result.functions.find((f) => f.functionName === 'interval'),
+          timestamp: coverage.timestamp
+        });
+      }
+    }
+  }
+
+  coverages = coverages.sort((a, b) => { return a.timestamp - b.timestamp; });
+  // There should be two coverages taken, one triggered by v8.takeCoverage(),
+  // the other by process exit.
+  console.log('Coverages:', coverages);
+  assert.strictEqual(coverages.length, 3);
+
+  let blockHitsTotal = 0;
+  for (let i = 0; i < coverages.length; ++i) {
+    const { ranges } = coverages[i].func;
+    console.log('coverage', i, ranges);
+
+    if (i !== coverages.length - 1) {
+      // When the first two coverages are taken:
+      assert.strictEqual(ranges.length, 2);
+      const blockHits = ranges[0].count;
+      // The block inside interval() should be hit at least once.
+      assert.notStrictEqual(blockHits, 0);
+      blockHitsTotal += blockHits;
+      // The else branch should not be hit.
+      const elseBranchHits = ranges[1].count;
+      assert.strictEqual(elseBranchHits, 0);
+    } else {
+      // At process exit:
+      assert.strictEqual(ranges.length, 3);
+      const blockHits = ranges[0].count;
+      // The block inside interval() should be hit at least once more.
+      assert.notStrictEqual(blockHits, 0);
+      blockHitsTotal += blockHits;
+      // The else branch should be hit exactly once.
+      const elseBranchHits = ranges[2].count;
+      assert.strictEqual(elseBranchHits, 1);
+      const ifBranchHits = ranges[1].count;
+      assert.strictEqual(ifBranchHits, blockHits - elseBranchHits);
+    }
+  }
+
+  // The block should be hit `intervals` times in total.
+  assert.strictEqual(blockHitsTotal, intervals);
+}