refactor: rename tests to better describe what they check for

I had trouble understanding what the different tests were meant to
check for, so I've renamed them into something (hopefully) more explanatory.

src/index.test.ts

@@ -1023,7 +1023,7 @@ test('Should pass under custom header clientKey', async () => {
     jest.advanceTimersByTime(999);
 });
 
-test('Should call isEnabled event when impressionData is true', (done) => {
+test('Should emit impression events on isEnabled checks when impressionData is true', (done) => {
     const bootstrap = [
         {
             name: 'impression',
@@ -1084,7 +1084,7 @@ test('Should pass custom headers', async () => {
     });
 });
 
-test('Should call getVariant event when impressionData is true', (done) => {
+test('Should emit impression events on getVariant calls when impressionData is true', (done) => {
     const bootstrap = [
         {
             name: 'impression-variant',
@@ -1120,7 +1120,7 @@ test('Should call getVariant event when impressionData is true', (done) => {
     });
 });
 
-test('Should not call isEnabled event when impressionData is false', (done) => {
+test('Should not emit impression events on isEnabled calls when impressionData is false', (done) => {
     const bootstrap = [
         {
             name: 'impression',
@@ -1155,7 +1155,7 @@ test('Should not call isEnabled event when impressionData is false', (done) => {
     });
 });
 
-test('Should call isEnabled event when impressionData is false and impressionDataAll is true', (done) => {
+test('Should emit impression events on isEnabled calls when impressionData is false and impressionDataAll is true', (done) => {
     const bootstrap = [
         {
             name: 'impression',
@@ -1197,7 +1197,7 @@ test('Should call isEnabled event when impressionData is false and impressionDat
     });
 });
 
-test('Should call isEnabled event when toggle is unknown and impressionDataAll is true', (done) => {
+test('Should emit impression events on isEnabled calls when toggle is unknown and impressionDataAll is true', (done) => {
     const bootstrap = [
         {
             name: 'impression',
@@ -1235,7 +1235,7 @@ test('Should call isEnabled event when toggle is unknown and impressionDataAll i
     });
 });
 
-test('Should call getVariant event when impressionData is false and impressionDataAll is true', (done) => {
+test('Should emit impression events on getVariant calls when impressionData is false and impressionDataAll is true', (done) => {
     const bootstrap = [
         {
             name: 'impression-variant',