diff --git a/tests/bar/1.0/default/Bar.cpp b/tests/bar/1.0/default/Bar.cpp
index 6a8a360..4614428 100644
--- a/tests/bar/1.0/default/Bar.cpp
+++ b/tests/bar/1.0/default/Bar.cpp
@@ -19,6 +19,11 @@
 }
 
 // Methods from ::android::hardware::tests::foo::V1_0::IFoo follow.
+Return<void> Bar::convertToBoolIfSmall(Discriminator d, const hidl_vec<Union>& u,
+                                       convertToBoolIfSmall_cb _hidl_cb) {
+    return mFoo->convertToBoolIfSmall(d, u, _hidl_cb);
+}
+
 Return<void> Bar::doThis(float param) {
     return mFoo->doThis(param);
 }
diff --git a/tests/bar/1.0/default/Bar.h b/tests/bar/1.0/default/Bar.h
index b276823..acb976f 100644
--- a/tests/bar/1.0/default/Bar.h
+++ b/tests/bar/1.0/default/Bar.h
@@ -31,6 +31,8 @@
     Bar();
 
     // Methods from ::android::hardware::tests::foo::V1_0::IFoo follow.
+    virtual Return<void> convertToBoolIfSmall(Discriminator d, const hidl_vec<Union>& u,
+                                              convertToBoolIfSmall_cb _hidl_cb) override;
     virtual Return<void> doThis(float param)  override;
     virtual Return<int32_t> doThatAndReturnSomething(int64_t param)  override;
     virtual Return<double> doQuiteABit(int32_t a, int64_t b, float c, double d)  override;
diff --git a/tests/foo/1.0/IFoo.hal b/tests/foo/1.0/IFoo.hal
index c1ce7b0..4a930a2 100644
--- a/tests/foo/1.0/IFoo.hal
+++ b/tests/foo/1.0/IFoo.hal
@@ -122,6 +122,19 @@
         bitfield<BitField> bf;
     };
 
+    enum Discriminator : uint8_t {
+        BOOL,
+        INT,
+    };
+    union Union {
+        bool boolValue;
+        int64_t intValue;
+    };
+    struct ContainsUnion {
+        Discriminator discriminator;
+        Union value;
+    };
+
     typedef int32_t[5][6][7] multidimArrayOne;
     typedef multidimArrayOne[8][9][10] multidimArrayTwo;
     typedef multidimArrayTwo[2][3][4] multidimArrayThree;
@@ -144,6 +157,16 @@
         InnerTestEnumTypedef foo;
     };
 
+    /**
+     * If d is INT, converts all values to bools which are small enough (0 or 1).
+     * If d is BOOL, should leave all values as BOOLs.
+     *
+     * @param d discriminator for all values in u
+     * @param u values to be expanded
+     * @return c must have same length as u unless there is an error in which case it will be empty.
+     */
+    convertToBoolIfSmall(Discriminator d, vec<Union> u) generates (vec<ContainsUnion> c);
+
     doThis(float param);
     doThatAndReturnSomething(int64_t param) generates (int32_t result);
     doQuiteABit(int32_t a, int64_t b, float c, double d) generates (double something);
diff --git a/tests/foo/1.0/default/Foo.cpp b/tests/foo/1.0/default/Foo.cpp
index a860ce7..a31ab9f 100644
--- a/tests/foo/1.0/default/Foo.cpp
+++ b/tests/foo/1.0/default/Foo.cpp
@@ -15,6 +15,30 @@
 namespace implementation {
 
 // Methods from ::android::hardware::tests::foo::V1_0::IFoo follow.
+Return<void> Foo::convertToBoolIfSmall(Discriminator d, const hidl_vec<Union>& u,
+                                       convertToBoolIfSmall_cb _hidl_cb) {
+    hidl_vec<ContainsUnion> res(u.size());
+    for (size_t i = 0; i < u.size(); i++) {
+        ContainsUnion& outValue = res[i];
+
+        if (d == Discriminator::BOOL) {
+            outValue.discriminator = Discriminator::BOOL;
+            outValue.value.boolValue = u[i].boolValue;
+        } else {
+            uint64_t value = u[i].intValue;
+            if (value == 0 || value == 1) {
+                outValue.discriminator = Discriminator::BOOL;
+                outValue.value.boolValue = static_cast<bool>(value);
+            } else {
+                outValue.discriminator = Discriminator::INT;
+                outValue.value.intValue = value;
+            }
+        }
+    }
+    _hidl_cb(res);
+    return Void();
+}
+
 Return<void> Foo::doThis(float param) {
     LOG(INFO) << "SERVER(Foo) doThis(" << param << ")";
 
diff --git a/tests/foo/1.0/default/Foo.h b/tests/foo/1.0/default/Foo.h
index 4558a73..7dd672b 100644
--- a/tests/foo/1.0/default/Foo.h
+++ b/tests/foo/1.0/default/Foo.h
@@ -22,9 +22,14 @@
 using ::android::hardware::hidl_vec;
 using ::android::hardware::hidl_string;
 using ::android::sp;
+using ContainsUnion = ::android::hardware::tests::foo::V1_0::IFoo::ContainsUnion;
+using Discriminator = ::android::hardware::tests::foo::V1_0::IFoo::Discriminator;
+using Union = ::android::hardware::tests::foo::V1_0::IFoo::Union;
 
 struct Foo : public IFoo {
     // Methods from ::android::hardware::tests::foo::V1_0::IFoo follow.
+    virtual Return<void> convertToBoolIfSmall(Discriminator d, const hidl_vec<Union>& u,
+                                              convertToBoolIfSmall_cb _hidl_cb) override;
     virtual Return<void> doThis(float param)  override;
     virtual Return<int32_t> doThatAndReturnSomething(int64_t param)  override;
     virtual Return<double> doQuiteABit(int32_t a, int64_t b, float c, double d)  override;